Method of manufacturing Fe-base soft magnetic alloy

ABSTRACT

The present invention relates to a method of stably manufacturing a Fe-base soft magnetic alloy having steps of subjecting an amorphous alloy mainly composed of Fe to heat treatment in which the amorphous alloy is heated to 400° to 750° C. at a heating rate of 1.0° C./minute or higher so that at least 50% or more of the structure of the amorphous alloy is made of fine crystalline grains formed into a body-centered cubic structure and having an average grain size of crystal of 30 nm or smaller as to have a high magnetic permeability and saturation magnetic flux density.

BACKGROUND OF THE INVENTION

The present invention relates to a method of manufacturing a softmagnetic alloy for use in a magnetic head, a transformer, or a chokecoil or the like, and more particularly to a method of manufacturing aFe-base soft magnetic alloy having a high saturation magnetic fluxdensity and excellent soft magnetic characteristics.

A soft magnetic alloy for use in a magnetic head, a transformer, or achoke coil or the like must have the following characteristics:

(1) high magnetic flux density;

(2) high magnetic permeability;

(3) small coercive force;

(4) low magnetostriction; and

(5) a thin shape which can easily be formed.

The magnetic head must have the following characteristics in order toimprove the wear resistance in addition to the foregoing characteristics(1) to (5):

(6) excellent hardness.

Therefore, materials for a variety of alloy systems have been studied tosatisfy the foregoing characteristics when a soft magnetic alloy or amagnetic head is manufactured. Hitherto, crystalline alloys such assendust, permalloy and iron-silicon steel and the like have beenemployed for use in the foregoing purposes. Recently, a Fe-base or aCo-base amorphous alloy has been used.

Under the foregoing circumstances, the magnetic head must be adaptableto a magnetic recording medium of a type having large coercive forcerequired to record information at a high density by employing furthersuitable magnetic material to form the magnetic head that exhibitsexcellent performance. Further, the size of the transformer and thechoke coil must be further reduced to be adaptable to the trend ofreducing electronic equipment by using magnetic material having furthersatisfactory performance.

However, sendust suffers from unsatisfactorily low saturation magneticflux density of about 11 KG although it has excellent soft magneticcharacteristics. Also permalloy encounters a problem of anunsatisfactorily low saturation magnetic flux density of about 8 KG whenit is formed into an alloy structure that exhibits excellent softmagnetic characteristics. The iron-silicon steel (Fe--Si Alloy) has aproblem of unsatisfactory soft magnetic characteristics although itexhibits a high saturation magnetic flux density.

As for the amorphous alloy, the Co-base alloy has an unsatisfactorysaturation magnetic flux density of about 10 KG although it hasexcellent soft magnetic characteristics. Although the Fe-base alloyexhibits a high saturation magnetic flux density of 15 KG or higher, theattained soft magnetic characteristics are unsatisfactory. The stabilityof the amorphous alloy against heat is insufficient, resulting in aproblem to be solved. Therefore, it is difficult to simultaneouslyrealize the high saturation magnetic flux density and excellent softmagnetic characteristics.

An alloy for a transformer having a high saturation magnetic fluxdensity and exhibiting a low core loss has been disclosed in U.S. Pat.No. 5,069,731, the composition of which is expressed by a generalformula:

    (Fe.sub.1-a M.sub.1a).sub.100-x-y-z-t Cu.sub.x Si.sub.y B.sub.z M.sub.2t

where M₁ is Co and/or, M₂ is at least one element selected from a groupconsisting of Nb, W, Ta, Mo, Zr, Hr and Ti, and a, x, y, z and trespectively satisfy, by atom %, 0≦a≦0.3, 0.1≦x≦3, 0≦y≦17, 4≦z≦17,10≦y+z≦28 and 0.1≦t≦5.

At least 50% of the structure is made of fine crystalline grains and theaverage grain size obtained by measuring the maximum crystalline grainis 1000 Å or less.

The foregoing fine crystalline alloy has been developed while making aFe--Si--B amorphous alloy, disclosed in U.S. Pat. No. 5,160,379, as astarting material. In the Fe--Si--B alloy, elements for making thestructure to be amorphous are Si and B and the content of Fe in an alloyhaving sufficient heat stability in terms of practical use is 70 to 80atom %. The foregoing amorphous alloy has magnetic characteristicssuperior to that of the conventional Fe--Si alloy (iron-silicon alloy).The fine crystalline alloy disclosed above is a Fe--M₁ --Cu--Si--B--M₃alloy made by adding Cu and M elements to a Fe--Si--B alloy, where theelement M₃ is at least one element selected from a group consisting ofNb, W, Ta, Zr, Hf, Ti and Mo.

It is necessary for the alloy of the foregoing type to contain Cubecause it has been said that the addition of Cu causes fluctuation tooccur in the amorphous to generate fine crystalline grains and,accordingly, the structure can be made fine. It has been disclosed inthe foregoing application that the omission of the addition of Cu cannoteasily produce fine crystalline grains, a compound phase can easily begenerated and therefore the magnetic characteristics deteriorate.

In the alloy of the foregoing system, the mutual action between Cu andNb is able to prevent the enlargement of the crystalline grains.Therefore, it has been considered that composite addition of Nb and Cuis required because sole addition of Nb or Cu cannot prevent theenlargement of the crystalline grains. The foregoing fact has beendisclosed by the inventors of the foregoing disclosure in Journal ofMaterials Transaction, JIM, Vol. 31, No. 4 (1990), pp. 307-314.

A fact can be understood from FIG. 20, which is a composition view, ofU.S. Pat. No. 5,160,379 that the low magnetostriction cannot be obtainedfrom the alloy of the foregoing system if Si=0. Since Si acts to reducethe magnetostriction, Si must be added to reduce the magnetostriction.

The inventors of the present invention have been developing softmagnetic material by using material of a component system which iscompletely different from an extremely different viewpoint. Amongothers, there is a Fe (Co, Ni)--Zr alloy system previously disclosed inU.S. Pat. No. 4,623,387 and 4,842,657 established while considering theconventional technologies about sendust, permalloy and iron-siliconsteel.

The Fe (Co, Ni)--Zr alloy system contains Zr having excellentperformance of forming amorphous added thereto and, accordingly,amorphous alloy can be formed even if the amount of the addition of Zris reduced. Therefore, the concentration of Fe can be made about 90% orhigher. Further, Hf can be used as an element for forming an amorphousalloy similar to Zr. However, the Curie temperature of the alloy of atype containing Fe at a high concentration is in the vicinity of theroom temperature and, therefore, the alloy of the foregoing type is nota practical alloy as the material for the magnetic core.

The inventors of the present invention have found a fact that partialcrystallization of Fe--Hf amorphous alloy by a special method enables afine crystalline structure having an average crystalline grain size ofabout 10 to 20 nm and disclosed this in "CONFERENCE ON METALLIC SCIENCEAND TECHNOLOGY BUDAPEST", 1980, p.p. 217 to 221. It can be consideredfrom the disclosed technology that fining of the structure of the Fe--Malloy can be enabled even if elements such as Cu are not added. Althoughthe mechanism of this has not been clarified yet, fluctuation of thestructure is already present in a rapidly solidified state in a casewhere the amorphous phase is formed and the fluctuation becomesnucleation site resulting in that a multiplicity of uniform and finenuclei are generated.

As described above, the Fe--M (Zr, Hf) alloy system do not haveexcellent magnetic characteristics in an amorphous state because oftheir low Curie temperatures. However, consideration of a fact that theforegoing alloy can be finely crystallized without addition of thenon-magnetic element resulted in that making of the Fe--M amorphousalloy to be a starting material enables a fine crystalline alloy to beobtained which contains a Fe at a concentration that is considerablyhigher than that of the conventional alloy and, therefore, an alloy canbe expected to be obtained which has a saturation magnetic flux densitywhich is higher than that of the conventional Fe--Si--B based finecrystalline alloy.

SUMMARY OF THE INVENTION

Accordingly, the inventors of the present invention have intenselystudied, resulting in that the grain enlargement can be prevented byimproving the heat stability of a Fe--M fine crystalline alloy. Further,an amorphous phase must be left in the grain boundary, the amorphousphase being a thermally stable which is able to serve as a barrier forthe grain coarsening. On the foregoing viewpoint, the study carried outwhile paying attention to B, which is an element capable of improvingthe thermal stability of the amorphous alloy, resulted in the presentinvention to be found.

An object of the present invention is to provide a method of stablymanufacturing a Fe-base soft magnetic alloy having high saturationmagnetic flux density and high magnetic permeability, and alsoexhibiting satisfactory mechanical strength and excellent thermalstability.

In order to achieve the foregoing object, according to one aspect of thepresent invention, there is provided a method of manufacturing a Fe-basesoft magnetic alloy comprising a step of: subjecting an amorphous alloymainly composed of Fe to heat treatment in which the amorphous alloy isheated at a heating rate of 1.0° C./minute or higher so that at least50% or more of the structure of the amorphous alloy is made of finecrystalline grains formed into a body-centered cubic structure andhaving an average grain size of crystal of 30 nm or smaller.

According to a second aspect of the present invention, there is provideda method of manufacturing a Fe-base soft magnetic alloy having anarrangement that the heat treatment is so arranged that the heating atthe heating rate is performed and then the temperature is maintained at400° to 750° C.

It is preferable that the method of manufacturing a Fe-base softmagnetic alloy is so arranged that the composition of the Fe-base softmagnetic alloy is as follows, that is, the first composition isexpressed by the following formula:

    Fe.sub.b B.sub.x M.sub.y

where M is one or more elements selected from a group consisting of Ti,Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf, b=75 to 93 atom%, x=0.5 to 10 atom % and y=4 to 9 atom %.

A second composition is expressed by:

    Fe.sub.b B.sub.x M.sub.y X.sub.u

where M is one or more elements selected from a group consisting of Ti,Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf, X is one or moreelements selected from a group consisting of Cr, Ru, Rh and Ir, b=75 to93 atom %, x=0.5 to 10 atom %, y=4 to 9 atom % and u≦5 atom %.

A third composition is expressed by:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M.sub.y

where Z is Co and/or Ni, M is one or more elements selected from a groupconsisting of Ti, Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf,a≦0.1, b=75 to 93 atom %, x=0.5 to 10 atom % and y=4 to 9 atom %.

A fourth composition is expressed by:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M.sub.y X.sub.u

where Z is Co and/or Ni, M is one or more elements selected from a groupconsisting of Ti, Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf,X is one or more elements selected from a group consisting of Cr, Ru, Rhand Ir, a≦0.1, b=75 to 93 atom %, x=0.5 to 10 atom % and y=4 to 9 atom%.

A fifth composition is expressed by:

    Fe.sub.b B.sub.x M'.sub.y

where M' is one or more elements selected from a group consisting of Ti,V, Nb, Ta, Mo and W and contains Nb, b=75 to 93 atom %, x=6.5 to 14 atom% and y=4 to 9 atom %.

A sixth composition is expressed by:

    Fe.sub.b B.sub.x M'.sub.y X.sub.u

where M' is one or more elements selected from a group consisting of Ti,V, Nb, Ta, Mo and W and contains Nb, X is one or more elements selectedfrom a group consisting of Cr, Ru, Rh and Ir, b=75 to 93 atom %, x=6.5to 14 atom %, y=4 to 9 atom % and u≦5 atom %.

A seventh composition is expressed by:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M'.sub.y

where Z is Co and/or Ni, M' is one or more elements selected from agroup consisting of Ti, V, Nb, Ta, Mo and W and contains Nb, a≦0.1, b=75to 93 atom %, x=6.5 to 14 atom % and y=4 to 9 atom %.

An eighth composition is expressed by:

    (Fe.sub.1-a z.sub.a).sub.b B.sub.x M'.sub.y X.sub.u

where Z is Co and/or Ni, M' is one or more elements selected from agroup consisting of Ti, V, Nb, Ta, Mo and W and contains Nb, X is one ormore elements selected from a group consisting of Cr, Ru, Rh and Ir,a≦0.1, b=75 to 93 atom %, x=6.5 to 14 atom %, y=4 to 9 atom % and u≦5atom %.

A ninth composition is expressed by:

    Fe.sub.b B.sub.x M.sub.y T.sub.z

where M is one or more elements selected from a group consisting of Ti,Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf, T is one or moreelements selected from a group consisting of Cu, Ag, Au, Pd, Pt and Bi,75≦ to ≦93 atom %, x=0.5 to 18 atom %, 4≦y≦10 atom % and z≦4.5 atom %.

A tenth composition is expressed by:

    Fe.sub.b B.sub.x M.sub.y T.sub.z X.sub.u

where M is one or more elements selected from a group consisting of Ti,Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf, T is one or moreelements selected from a group consisting of Cu, Ag, Au, Pd, Pt and Bi,X is one or more elements selected from a group consisting of Cr, Ru, Rhand Ir, b≦75 to 93 atom %, x=0.5 to 18 atom %, y=4 to 10 atom %, z≦4.5atom % and u≦5.0 atom %.

An eleventh composition is expressed by:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M.sub.y T.sub.z

where Z is Co and/or Ni, M is one or more elements selected from a groupconsisting of Ti, Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf,T is one or more elements selected from a group consisting of Cu, Ag,Au, Pd, Pt and Bi, a≦0.1, 75≦b≦93 atom %, x=0.5 to 18 atom %, y=4 to 10atom % and z≦4.5 atom %.

A twelfth composition is expressed by:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M.sub.y T.sub.z X.sub.u

where Z is Co and/or Ni, M is one or more elements selected from a groupconsisting of Ti, Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf,T is one or more elements selected from a group consisting of Cu, Ag,Au, Pd, Pt and Bi, X is one or more elements selected from a groupconsisting of Cr, Ru, Rh and Ir, a≦0.1, 75≦b≦93 atom %, x=0.5 to 18 atom%, y=4 to 10 atom %, z≦4.5 atom % and u≦5 atom %.

A thirteenth composition is expressed by:

    Fe.sub.b B.sub.x M'.sub.y T.sub.z

where M' is one or more elements selected from a group consisting of Ti,V, Nb, Ta, Mo and W and contains any one of Ti, Nb and Ta, T is one ormore elements selected from a group consisting of Cu, Ag, Au, Pd, Pt andBi, 75≦b≦93 atom %, x=6.5 to 18 atom %, y=4 to 10 atom % and z≦4.5 atom%.

A fourteenth composition is expressed by:

    Fe.sub.b B.sub.x M'.sub.y T.sub.z X.sub.u

where M' is one or more elements selected from a group consisting of Ti,V, Nb, Ta, Mo and W and contains any one of Ti, Nb and Ta, T is one ormore elements selected from a group consisting of Cu, Ag, Au, Pd, Pt andBi, X is one or more elements selected from a group consisting of Cr,Ru, Rh and Ir, 75≦b≦93 atom %, x=6.5 to 18 atom %, y=4 to 10 atom %,z≦4.5 atom % and u≦5 atom %.

A fifteenth composition is expressed by:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M'.sub.y T.sub.z

where Z is Co and/or Ni, M' is one or more elements selected from agroup consisting of Ti, V, Nb, Ta, Mo and W and contains any one of Ti,Nb and Ta, T is one or more elements selected from a group consisting ofCu, Ag, Au, Pd, Pt and Bi, a≦0.1, 75≦b≦93 atom % , x=6.5 to 18 atom %,y=4 to 10 atom % and z≦4.5 atom %.

A sixteenth composition is expressed by:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M'.sub.y T.sub.z X.sub.u

where Z is Co and/or Ni, M' is one or more elements selected from agroup consisting of Ti, V, Nb, Ta, Mo and W and contains any one of Ti,Nb and Ta, T is one or more elements selected from a group consisting ofCu, Ag, Au, Pd, Pt and Bi, X is one or more elements selected from agroup consisting of Cr, Ru, Rh and Ir, a≦0.1, 75≦b≦93 atom %, x=6.5 to18 atom %, y=4 to 10 atom %, z≦4.5 atom % and u≦5 atom %.

It is further preferable that the ninth to sixteenth compositions be soarranged that z=0.2 to 4.5 atom %.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a double logarithmic graph which shows the relationship betweenthe heating rate and the magnetic permeability of an example of an alloyaccording to the present invention;

FIG. 2 is a graph which shows both the relationship between thesaturation magnetic flux density and the annealing temperature and therelationship between the effective magnetic permeability and theannealing temperature of the example of an alloy according to thepresent invention;

FIG. 3 is a graph which shows results of an X-ray diffractometry showingthe structural change of an alloy according to the present inventiontaken place before and after the heat treatment;

FIG. 4 is a schematic view of a microscope photograph showing thestructure of an example of an alloy according to the present inventionafter the heat treatment has been performed;

FIG. 5 is a triangular composition view which shows the magneticpermeability of an example of an alloy system according to the presentinvention subjected to isothermal annealing for 1 hour at 600° C. in acase where the quantities of Zr, B and Fe are changed;

FIG. 6 is a triangular composition view which shows the magneticpermeability of an example of an alloy system according to the presentinvention subjected to isothermal annealing for 1 hour at 650° C. in acase where the quantities of Zr, B and Fe are changed;

FIG. 7 is a triangular composition view which shows the saturationmagnetic flux density in a case where the quantities of Zr, B and Fe arechanged;

FIG. 8 is a triangular composition view which shows the saturationmagnetic flux density in a case where the quantities of Zr, B and Fe arechanged;

FIG. 9 is a single logarithmic graph which shows the relationshipbetween the quantity of Co or that of Ni and the magnetic permeabilityof an example of an alloy system according to the present invention;

FIG. 10 is a graph which shows the relationship between the effectivemagnetic permeability and the annealing temperature of an example of analloy according to the present invention;

FIG. 11 is a graph which shows results of an X-ray diffractometryshowing the structural change of an alloy according to the presentinvention taken place before and after the heat treatment;

FIG. 12 is a schematic view of a microscope photograph showing thestructure of an example of an alloy according to the present inventionafter the heat treatment has been performed;

FIG. 13 is a triangular composition view which shows an example of analloy system according to the present invention in a case where thequantities Fe+Cu, the quantity of B and that of Zr are changed;

FIG. 14 is a single logarithmic graph which shows the relationshipbetween the quantity of Hf and the magnetic permeability of an alloysystem according to the present invention;

FIG. 15 is a triangle composition view which shows the magneticcharacteristics of an alloy system according to the present invention ina case where the quantity of B, the quantity of Zr+Nb and the quantityof Fe+Cu are changed;

FIG. 16 is a single logarithmic graph which shows the relationshipbetween the quantity of Cu and the effective magnetic permeability of anexample of an alloy system according to the present invention;

FIG. 17 is a single logarithmic graph which shows the relationshipbetween the quantity of Co and the magnetic permeability of an exampleof an alloy system according to the present invention;

FIG. 18 is a graph which shows the relationship between the effectivepermeability and the annealing temperature of an example of an alloyaccording to the present invention;

FIG. 19 is a single logarithmic graph which shows the relationshipbetween the quantity of B and the effective magnetic permeability of anexample of an alloy system according to the present invention;

FIG. 20 is a single logarithmic graph which shows the relationshipbetween the quantity of Nb and the effective magnetic permeability of anexample of an alloy system according to the present invention;

FIG. 21 is a graph which shows results of an X-ray diffractometryshowing the structural change of an alloy according to the presentinvention taken place before and after the heat treatment;

FIG. 22 is a schematic view of a microscope photograph showing thestructure of an example of an alloy according to the present inventionafter the heat treatment has been performed;

FIG. 23 is a triangle composition view which shows the magneticpermeability of an example of an alloy system according to the presentinvention in a case where the quantity of Fe+Cu, the quantity of B andthat of Nb are changed;

FIG. 24 is a triangle composition view which shows the saturationmagnetic flux density of an alloy system according to the presentinvention in a case where the quantity of Fe+Cu, the quantity of B andthat of Nb are changed;

FIG. 25 is a single logarithmic graph which illustrates the quantity ofCu and the effective magnetic permeability of an example of an alloysystem according to the present invention;

FIG. 26 is a single logarithmic graph which shows the relationshipbetween the quantities of Nb, Ta and Ti and the magnetic permeability ofan example of the alloy systems according to the present invention;

FIG. 27 is a graph which shows both the relationship between thesaturation magnetic flux density and the annealing temperature and therelationship between the effective magnetic permeability and theannealing temperature of an example of an alloy according to the presentinvention;

FIG. 28 is a single logarithmic graph which shows the relationshipbetween the quantity of B and the effective magnetic permeability of anexample of an alloy system according to the present invention;

FIG. 29 is a graph which shows results of an X-ray diffractometryshowing the structural change of an alloy according to the presentinvention taken place before and after the heat treatment;

FIG. 30 is a schematic view of a microscope photograph showing thestructure of an example of an alloy according to the present inventionafter the heat treatment has been performed;

FIG. 31 is a triangle composition view which shows the saturationmagnetic flux density of an example of an alloy system according to thepresent invention in a case where the quantities Fe, B and Nb arechanged;

FIG. 32 is a single logarithmic graph which shows the relationshipbetween the quantity of Co or that of Ni and the magnetic permeabilityof an example of an alloy system according to the present invention;

FIG. 33 (a) is a graph which shows the relationship between the quantityof Co and the saturation magnetic flux density of an example of an alloysystem according to the present invention;

FIG. 33 (b) is a graph which shows the relationship between the quantityof Co and the magnetostriction of an example of an alloy systemaccording to the present invention;

FIG. 33 (c) is a graph which shows the relationship between the quantityof Co and the magnetic permeability of an example of an alloy systemaccording to the present invention;

FIG. 34 is a graph which shows the relationship between the core lossand the maximum magnetic induction of an example of an alloy accordingto the present invention;

FIG. 35 is a graph which shows the relationship between the heating rateand the magnetic permeability of a first example of the alloy systemsaccording to the present invention;

FIG. 36 is a graph which shows the relationship between the heating rateand the magnetic permeability of a second example of the alloy systemsaccording to the present invention;

FIG. 37 is a graph which shows the relationship between the heating rateand the magnetic permeability of a third example of the alloy systemsaccording to the present invention;

FIG. 38 is a graph which shows the relationship between the heating rateand the magnetic permeability of a fourth example of the alloy systemsaccording to the present invention;

FIG. 39 is a plot of the data shown in Table 18, showing therelationship between the average grain size and the coercive force ofthe example of the alloy systems according to the present invention;

FIG. 40 is a graph which shows the fraction transformed for thecrystallization reaction of an example of an alloy according to thepresent invention;

FIG. 41 is a graph which illustrates a JMA plot of the example shown inFIG. 40;

FIG. 42 is a graph which shows the size distribution of the bcc grainsof an example of an alloy according to the present invention;

FIG. 43 is a graph which shows the size distribution of the bcc grainsof a comparative example of an alloy according to the present invention;

FIG. 44 is a schematic view of an electron microscope photograph whichshows the results of tests carried out for determining the size of thebcc grains of an alloy subjected to heat treatment set to a heating rateof 200° C./minute according to the present invention; and

FIG. 45 is a schematic view of a microscope photograph which shows theresults of tests carried out for determining the size of the bcc grainsof an alloy subjected to heat treatment set to a heating rate of 2.5°C./minute according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described in detail.

A Fe-base soft magnetic alloy according to the present invention can beusually obtained by a process in which the amorphous alloy having theforegoing composition or a crystalline alloy including an amorphousphase is rapidly cooled from a melted state, a process in which the sameis obtained by a rapid cooling method, such as a sputtering method or anevaporation method, and a heat treatment process in which the materialobtained by the foregoing processes is annealed for formation of finecrystalline grains through crystallization of an amorphous phase. Thematerial obtained by the foregoing rapid cooling method may be formedinto a ribbon or powder. The heat treatment may, of course, be performedafter the obtained material has been molded or machined into a desiredshape.

When the soft magnetic alloy according to the present invention ismanufactured, the material obtained by the rapid cooling method must besubjected to heat treatment in which it is heated at a desired heatingrate, the temperature is maintained at a predetermined temperaturerange, and the material is cooled. It is preferable that the heattreatment temperature be 400° to 750° C. It is also preferable that theheating rate at the time of performing the heat treatment is 1.0°C./minute or higher. The inventors of the present invention found thatthe heating rate at the time of performing the heat treatment affectsthe magnetic permeability of the soft magnetic alloy subjected to theheat treatment. By determining the heating rate to be 1.0° C./minute orhigher, a soft magnetic alloy having a high magnetic permeability canstably be manufactured.

The "heating rate" is a value obtained by, with time, differentiatingthe time change which takes from a moment at which an alloy to beprocessed is injected into a heating furnace, to a moment at which apredetermined heat treatment temperature is realized.

The soft magnetic alloy according to an embodiment of the presentinvention necessarily contains B added thereto. Boron has an effect ofimproving the performance of the soft magnetic alloy for formingamorphous alloys and an effect of improving the thermal stability of aFe--M (=Zr, Hf, Nb or the like) microcrystalline alloy to serve as abarrier against the grain coarsening. Further, it has an effect ofleaving an amorphous phase, which is thermally stable, in the grainboundary. As a result, a structure mainly composed of fine crystallinegrains having a grain size of 30 nm or less and formed into abody-centered cubic structure (bcc structure) can be obtained in theforegoing heat treatment under a wide heat treatment condition from 400°to 750° C., the grain size of 30 nm being the size that does notadversely affect the magnetic characteristics. Similarly to B, Al, Si, Cand P and the like are usually used as elements for forming amorphousstructure. The arrangements to which the foregoing elements are addedcan be considered to be the same as the present invention.

The soft magnetic alloy according to a first aspect of the presentinvention must contain Zr or Hf exhibiting the performance of formingthe amorphous structure in order to easily obtain the amorphous phase. Aportion of Zr and that of Hf may be substituted by Ti, V, Nb, Ta, Mo orW among group 4A to 6A elements of the periodic table. In this case thequantity of B is 0.5 to 10 atom % or the same is 0.5 to 18 atom % ifelement T is contained to obtain satisfactory performance of forming theamorphous structure. By dissolving Zr and Hf, which are elements thatare not dissolved in Fe in the equilibrium state, the magnetostrictioncan be reduced. That is, the dissolved quantity of Zr and Hf can beadjusted by the heat treatment conditions. Therefore, themagnetostriction can be adjusted and reduced.

Hence, a low magnetostriction can be obtained by obtaining finecrystalline structure under wide heat treatment conditions. The factthat the fine crystalline structure can be obtained under the wide heattreatment conditions by adding B enables both reduced magnetostrictionand small magnetocrystalline anisotropy to be possessed, resulting inthat excellent magnetic characteristics can be obtained.

If Cr, Ru, Rh or Ir is added to the foregoing composition if necessary,the corrosion resistance can be improved. In order to maintain thesaturation magnetic flux density at 10 kG or more, the quantity of theelement added must be 5 atom % or less.

The capability that a fine crystalline structure can be obtained bypartially crystallizing the Fe--M (=Zr, Hf) amorphous alloy by a specialmethod has been disclosed by the inventors of the present invention onp.p. 217 to 221 of "CONFERENCE ON METALLIC SCIENCE AND TECHNOLOGYBUDAPEST", 1980. A fact has been found due to the studies made sincethen that the compositions disclosed this time enables a similar effectto be obtained, resulting in the present invention. The reason why thefine crystalline structure can be obtained is that fluctuation of thecomposition takes place in the rapidly solidified state in the processfor forming the amorphous phase for manufacturing the alloy, thefluctuation brings about an increase of the frequency of nucleationresulting in a multiplicity of uniform and fine nuclei to be generated.

The content of Fe in the soft magnetic alloys according to theembodiment of the present invention or the quantity of Fe, Co or Ni is93 atom %. If the content is larger than 93 atom %, a high magneticpermeability cannot be obtained. However, it is preferable that thecontent be 75 atom % or more in order to obtain a saturation magneticflux density of 10 kG or more.

It is preferable that the soft magnetic alloys according to a secondaspect of the present invention contain one or more elements selectedfrom a group consisting of Cu, its homolog elements Ag, Au, Pd, Pt andBi by a quantity of 4.5 atom % or less. If the quantity of addition ofthe elements is smaller than 0.2 atom %, excellent soft magneticcharacteristics cannot easily be obtained from the foregoing heattreatment process. By raising the heating rate, the magneticpermeability can be improved and the saturation magnetic flux densitycan be somewhat improved. Therefore, the contents of the foregoingelements may be made 0.2 atom % or less. By determining the contents ofthe foregoing elements to be 0.2 to 4.5 atom %, excellent soft magneticcharacteristics can be obtained even if the heating rate is not raisedconsiderably. Therefore, it is further preferable that the content of0.2 to 4.5 atom % be employed.

Among the foregoing elements, Cu is very effective. Although a mechanismof considerably improving the soft magnetic characteristics by theaddition of Cu or Pd has not been clarified yet, measurements of thecrystallizing temperature by a differential thermal analysis methodresulted a fact to be confirmed that the crystallization temperature ofthe alloy, to which Cu or Pd is added, is somewhat lower than that of analloy to which Cu or Pd is not added. It can be considered that theaddition of the foregoing element enhances the fluctuation in theamorphous phase, causing the stability of the amorphous phase todeteriorate. As a result, the crystalline phase can easily beprecipitated.

If nonhomogeneous amorphous phase is crystallized, a multiplicity ofregions, in which partial crystallization can easily be taken place, aregenerated and, accordingly, a large number of nuclei are generated.Therefore, the obtainable structure is made to be fine crystalline grainstructure, causing excellent magnetic characteristics to be obtained. Ifthe heating rate is further raised, formation of the fine crystallinestructure is enhanced. Therefore, if the heating rate is very high,element Cu or Pd may be contained by a quantity smaller than 0.2 atom %.Since Cu is an element which displays very low solid solubility withrespect to Fe and which therefore shows a phase separation tendency, themicro-structure encounters fluctuation due to heat application.Therefore, the tendency of the nonhomogeneity in amorphous phase isfurther enhanced, resulting in contribution to refine down thestructure. Therefore, elements capable of lowering the crystallizationtemperature are expected to enable a similar effect to be obtained aswell as Cu, its homolog element, Pd and Pt. Further, an element, such asBi, having a small solid solubility with respect to Fe, is, as well asCu, expected to enable a similar effect to be obtained.

In order to cause the soft magnetic alloys according to a third aspectof the present invention to easily obtain the amorphous phase, Nb and Bmust be contained which has performance for forming the amorphousstructure.

Among a group consisting of Ti, V, Ta, Mo and W, each of which enables asimilar effect to be obtained, V, Nb and Mo displays a restrictedtendency of generating an oxide and, accordingly, a satisfactorymanufacturing yield can be realized. Therefore, the addition of theforegoing element relaxes the manufacturing conditions, themanufacturing cost can be reduced and therefore an advantage can beobtained in the cost reduction. Specifically, while partially supplyinginactive gas to the leading portion of the nozzle, manufacturing can beperformed in the atmosphere or under the ambience of the atmosphere.

However, since the foregoing elements suffers from unsatisfactoryperformance of forming the amorphous structure as compared with Zr andHf, the soft magnetic alloys according to the third aspect are soarranged that the quantity of B is increased and its limit is made to be6.5 atom %. If element T is added, the effect obtainable from theaddition of T enables the upper limit of the quantity of B can be set to18 atom %. However, if T is not added, the magnetic characteristicsdeteriorate in a case where the quantity is larger than 14 atom %.Therefore, the upper limit in this case is determined to be 14 atom %.

The reason why the alloy elements contained in the soft magnetic alloyaccording to the present invention is as described above. A platinumgroup element, such as Ru, Rh or Ir or Cr may be added in order toimprove the corrosion resistance as well as the foregoing elements. Ifnecessary, Y, a rare earth metal, Zn, Cd, Ga, In, Ge, Sn, Pb, As, Sb,Se, Te, Li, Be, Mg, Ca, Sr or Ba or the like may be added to adjust themagnetostriction. As for the unavoidable impurity such as H, N, O or Sor the like, a composition which contains it by a quantity that does notdeteriorate the desired characteristics can, of course, be considered tobe the same as the composition of the Fe-base soft magnetic alloyaccording to the present invention.

EXAMPLES

Alloys according to the following examples were manufactured by a singleroller melt spinning method. Namely, melted alloy is, by the pressure ofargon gas, jetted out from a nozzle placed on one rotating Cu or steelroll onto the foregoing roll, and the temperature is rapidly lowered sothat a ribbon is obtained. The ribbon thus made has a width of about 15mm and a thickness of about 8 to 40 μm.

The magnetic permeability was measured in such a manner that theforegoing ribbon was machined to be formed into an annular shape having,in Examples 1 to 17, an outer diameter of 10 mm and an inner diameter of6 mm, then a coil is formed around a structure formed by stacking theforegoing annular members and an inductance method was employed tomeasure the magnetic permeability.

Example 1

The relationship between the heating rate at the time of the heattreatment and the magnetic permeability of a soft magnetic alloyobtained after the foregoing heat treatment had been performed wasexamined. The examinations were performed such that the heat treatmentwas applied to the alloys respectively having the compositions shown inTable 1 while changing the heating rate (°C./minute), and the magneticpermeability (μ) of the alloy applied with the heat treatment wasmeasured. The heat treatment was performed under the followingconditions: an infrared-ray image furnace was used; and a temperature of650° C. is maintained for one hour in a vacuum atmosphere. The coolingrate after the heat treatment had been performed was made to be aconstant rate of 10° C./minute. The magnetic permeability was measuredby using an impedance analyzer under conditions of 1 kHz and 0.4 A/m (5mOe). Results of the foregoing measurements are shown in Table 1 andFIG. 1.

Further, the relationship between the various heating rate and themagnetic permeabilities of the alloys was obtained by measuring themagnetic permeability of the samples subjected to isothermal annealingat a temperature of Ta for 1 hour. Table 2 shows the results of themeasurements of the magnetic permeabilities of the samples in a casewhere the heating rate was made to be 0.5° C./minute. Table 3 shows theresults of the measurements of the magnetic permeabilities of thesamples, the compositions of which are the same as those of the samplesshown in Table 2, in a case where the heating rate was made to be 5°C./minute. Table 4 shows the results of the measurements of the magneticpermeabilities of the samples, the compositions of which are the same asthose of the samples shown in Table 2, in a case where the heating ratewas made to be 80° C./minute. Table 5 shows the results of themeasurements of the magnetic permeabilities of the samples, thecompositions of which are the same as those of the samples shown inTable 2, in a case where the heating rate was made to be 160° C./minute.The residual measuring conditions were the same as those of theforegoing measurements.

                                      TABLE 1                                     __________________________________________________________________________    Temperature                                                                   Raising                                                                       Speed  Fe.sub.90 Zr.sub.7 B.sub.3                                                          Fe.sub.89 Zr.sub.7 B.sub.4                                                           Fe.sub.89 Zr.sub.6 B.sub.5                                                          Fe.sub.89 Hf.sub.7 B.sub.4                                                           Fe.sub.84 Nb.sub.7 B.sub.9                   __________________________________________________________________________    0.5    1800                4500   5500                                        1.5    5100                8800  12100                                        2.5    5000               11700  14300                                        5      6800   5600        13600  17500                                        10     7400          9200 13400  23000                                        40     15100 10900        21500  17300                                        100    19000              20600  23500                                        200    22000 15000  18400 32000  24000                                        __________________________________________________________________________

                  TABLE 2                                                         ______________________________________                                        Sample                                                                        No.    Composition of Alloy (at %)                                                                     Ta (°C.)                                                                         μ(1 kHz)                                ______________________________________                                         1     Fe.sub.91 Zr.sub.7 B.sub.2                                                                      650       2100                                        2     Fe.sub.90 Zr.sub.7 B.sub.3                                                                      650       1800                                        3     (Fe.sub.99.5 Co.sub.0.5).sub.90 Zr.sub.7 B.sub.3                                                650       1810                                        4     (Fe.sub.99 Co.sub.1).sub.90 Zr.sub.7 B.sub.3                                                    650       2250                                        5     (Fe.sub.98.5 Co.sub.1.5).sub.90 Zr.sub.7 B.sub.3                                                650       1840                                        6     (Fe.sub.98 Co.sub.2).sub.90 Zr.sub.7 B.sub.3                                                    650       1780                                        7     (Fe.sub.95 Co.sub.5).sub.90 Zr.sub.7 B.sub.3                                                    650       1690                                        8     (Fe.sub.99.5 Ni.sub.0.5).sub.90 Zr.sub.7 B.sub.3                                                600       1450                                        9     (Fe.sub.95 Ni.sub.5).sub.90 Zr.sub.7 B.sub.3                                                    600       1900                                       10     Fe.sub.89 Zr.sub.7 B.sub.3 Cu.sub.1                                                             600       14500                                      11     Fe.sub.89 Zr.sub.7 B.sub.3 Ru.sub.1                                                             600       1760                                       12     Fe.sub.89.5 Zr.sub.7 B.sub.3 Pd.sub.0.5                                                         650       2400                                       13     Fe.sub.89 Zr.sub.7 B.sub.3 Pd.sub.1                                                             650       5010                                       14     (Fe.sub.99 Co.sub.1).sub.84 Nb.sub.7 B.sub.9                                                    650       5850                                       15     (Fe.sub.95 Co.sub.5).sub.84 Nb.sub.7 B.sub.9                                                    650       4670                                       16     (Fe.sub.99 Ni.sub.1).sub.84 Nb.sub.7 B.sub.9                                                    650       5160                                       17     Fe.sub.81 Ti.sub.7 B.sub.11 Cu.sub.1                                                            600       7300                                       18     Fe.sub.81 Ta.sub.7 B.sub.11 Cu.sub.1                                                            600       6620                                       19     Fe.sub.87 Ti.sub.1 Zr.sub.2 Hf.sub.2 V.sub.1 Nb.sub.1 B.sub.6                                   600       3720                                       20     Fe.sub.89 Zr.sub.7 B.sub.3 Bi.sub.1                                                             600       1520                                       21     (Fe.sub.99 Ni.sub.1).sub.90 Zr.sub.7 B.sub.3                                                    600       1590                                       ______________________________________                                         Heating rate: 0.5° C./m                                                Shape of sample: annular (inner diameter: 6 mm, outer diameter: 10 mm)        Measuring magnetic field: 5 mOe                                          

                  TABLE 3                                                         ______________________________________                                        Sample                                                                        No.    Composition of Alloy (at %)                                                                     Ta (°C.)                                                                         μ(1 kHz)                                ______________________________________                                        22     Fe.sub.91 Zr.sub.7 B.sub.2                                                                      650       4700                                       23     Fe.sub.90 Zr.sub.7 B.sub.3                                                                      650       6800                                       24     (Fe.sub.99.5 Co.sub.0.5).sub.90 Zr.sub.7 B.sub.3                                                650       4000                                       25     (Fe.sub.99 Co.sub.1).sub.90 Zr.sub.7 B.sub.3                                                    650       4100                                       26     (Fe.sub.98.5 Co.sub.1.5).sub.90 Zr.sub.7 B.sub.3                                                650       4700                                       27     (Fe.sub.98 Co.sub.2).sub.90 Zr.sub.7 B.sub.3                                                    650       5000                                       28     (Fe.sub.95 Co.sub.5).sub.90 Zr.sub.7 B.sub.3                                                    650       4400                                       29     (Fe.sub.99.5 Ni.sub.0.5).sub.90 Zr.sub.7 B.sub.3                                                600       6100                                       30     (Fe.sub.95 Ni.sub.5).sub.90 Zr.sub.7 B.sub.3                                                    600       7900                                       31     Fe.sub.89 Zr.sub.7 B.sub.3 Cu.sub.1                                                             600       20400                                      32     Fe.sub.89 Zr.sub.7 B.sub.3 Ru.sub.1                                                             600       5600                                       33     Fe.sub.89.5 Zr.sub.7 B.sub.3 Pd.sub.0.5                                                         650       7400                                       34     Fe.sub.89 Zr.sub.7 B.sub.3 Pd.sub.1                                                             650       9300                                       35     (Fe.sub.99 Co.sub.1).sub.84 Nb.sub.7 B.sub.9                                                    650       9100                                       36     (Fe.sub.95 Co.sub.5 ).sub.84 Nb.sub.7 B.sub.9                                                   650       5010                                       37     (Fe.sub.99 Ni.sub.1).sub.84 Nb.sub.7 B.sub.9                                                    650       7900                                       38     Fe.sub.81 Ti.sub.7 B.sub.11 Cu.sub.1                                                            600       8100                                       39     Fe.sub.81 Ta.sub.7 B.sub.11 Cu.sub.1                                                            600       8200                                       40     Fe.sub.87 Ti.sub.1 Zr.sub.2 Hf.sub.2 V.sub.1 Nb.sub.1 B.sub.6                                   600       5500                                       41     Fe.sub.89 Zr.sub.7 B.sub.3 Bi.sub.1                                                             600       5600                                       42     (Fe.sub.99 Ni.sub.1).sub.90 Zr.sub.7 B.sub.3                                                    600       6800                                       ______________________________________                                         Heating rate: 5° C./m                                                  Shape of sample: annular (inner diameter: 6 mm, outer diameter: 10 mm)        Measuring magnetic field: 5 mOe                                          

                  TABLE 4                                                         ______________________________________                                        Sample                                                                        No.    Composition of Alloy (at %)                                                                     Ta (°C.)                                                                         μ(1 kHz)                                ______________________________________                                        43     Fe.sub.91 Zr.sub.7 B.sub.2                                                                      650       17900                                      44     Fe.sub.90 Zr.sub.7 B.sub.3                                                                      650       19200                                      45     (Fe.sub.99.5 Co.sub.0.5).sub.90 Zr.sub.7 B.sub.3                                                650       24300                                      46     (Fe.sub.99 Co.sub.1).sub.90 Zr.sub.7 B.sub.3                                                    650       17300                                      47     (Fe.sub.98.5 Co.sub.1.5).sub.90 Zr.sub.7 B.sub.3                                                650       18100                                      48     (Fe.sub.98 Co.sub.2).sub.90 Zr.sub.7 B.sub.3                                                    650       18400                                      49     (Fe.sub.95 Co.sub.5).sub.90 Zr.sub.7 B.sub.3                                                    650        8220                                      50     (Fe.sub.99.5 Ni.sub.0.5).sub.90 Zr.sub.7 B.sub.3                                                600       28000                                      51     (Fe.sub.95 Ni.sub.5).sub.90 Zr.sub.7 B.sub.3                                                    600        9040                                      52     Fe.sub.89 Zr.sub.7 B.sub.3 Cu.sub.1                                                             600       45200                                      53     Fe.sub.89 Zr.sub.7 B.sub.3 Ru.sub.1                                                             600       16200                                      54     Fe.sub.89.5 Zr.sub.7 B.sub.3 Pd.sub.0.5                                                         650       17700                                      55     Fe.sub.89 Zr.sub.7 B.sub.3 Pd.sub.1                                                             650       20800                                      56     (Fe.sub.99 Co.sub.1).sub.84 Nb.sub.7 B.sub.9                                                    650       14700                                      57     (Fe.sub.95 Co.sub. 5).sub.84 Nb.sub.7 B.sub.9                                                   650        8520                                      58     (Fe.sub.99 Ni.sub.1).sub.84 Nb.sub.7 B.sub.9                                                    650       14800                                      59     Fe.sub.81 Ti.sub.7 B.sub.11 Cu.sub.1                                                            600       16500                                      60     Fe.sub.81 Ta.sub.7 B.sub.11 Cu.sub.1                                                            600       14500                                      61     Fe.sub.87 Ti.sub.1 Zr.sub.2 Hf.sub.2 V.sub.1 Nb.sub.1 B.sub.6                                   600        9130                                      62     Fe.sub.89 Zr.sub.7 B.sub.3 Bi.sub.1                                                             600       16500                                      63     (Fe.sub.99 Ni.sub.1).sub.90 Zr.sub.7 B.sub.3                                                    600       23400                                      ______________________________________                                         Heating rate: 80° C./m                                                 Shape of sample: annular (inner diameter: 6 mm, outer diameter: 10 mm)        Measuring magnetic field: 5 mOe                                          

                  TABLE 5                                                         ______________________________________                                        Sample                                                                        No.    Composition of Alloy (at %)                                                                     Ta (°C.)                                                                         μ(1 kHz)                                ______________________________________                                        64     Fe.sub.91 Zr.sub.7 B.sub.2                                                                      650       18700                                      65     Fe.sub.90 Zr.sub.7 B.sub.3                                                                      650       24100                                      66     (Fe.sub.99.5 Co.sub.0.5).sub.90 Zr.sub.7 B.sub.3                                                650       27000                                      67     (Fe.sub.99 Co.sub.1).sub.90 Zr.sub.7 B.sub.3                                                    650       22100                                      68     (Fe.sub.98.5 Co.sub.1.5).sub.90 Zr.sub.7 B.sub.3                                                650       23300                                      69     (Fe.sub.98 Co.sub.2).sub.90 Zr.sub.7 B.sub.3                                                    650       19600                                      70     (Fe.sub.95 Co.sub.5).sub.90 Zr.sub.7 B.sub.3                                                    650       10300                                      71     (Fe.sub.99.5 Ni.sub.0.5).sub.90 Zr.sub.7 B.sub.3                                                600       17300                                      72     (Fe.sub.95 Ni.sub.5).sub.90 Zr.sub.7 B.sub.3                                                    600       18700                                      73     Fe.sub.89 Zr.sub.7 B.sub.3 Cu.sub.1                                                             600       44200                                      74     Fe.sub.89 Zr.sub.7 B.sub.3Ru.sub.1                                                              600       19800                                      75     Fe.sub.89.5 Zr.sub.7 B.sub.3 Pd.sub.0.5                                                         650       22000                                      76     Fe.sub.89 Zr.sub.7 B.sub.3 Pd.sub.1                                                             650       22400                                      77     (Fe.sub.99 Co.sub.1).sub.84 Nb.sub.7 B.sub.9                                                    650       18300                                      78     (Fe.sub.95 Co.sub.5).sub.84 Nb.sub.7 B.sub.9                                                    650        9750                                      79     (Fe.sub.99 Ni.sub.1).sub.84 Nb.sub.7 B.sub.9                                                    650       16100                                      80     Fe.sub.81 Ti.sub.7 B.sub.11 Cu.sub.1                                                            600       16800                                      81     Fe.sub.81 Ta.sub.7 B.sub.11 Cu.sub.1                                                            600       16500                                      82     Fe.sub.87 Ti.sub.1 Zr.sub.2 Hf.sub.2 V.sub.1 Nb.sub.1 B.sub.6                                   600       10800                                      83     Fe.sub.89 Zr.sub.7 B.sub.3 Bi.sub.1                                                             600       18900                                      84     (Fe.sub.99 Ni.sub.1).sub.90 Zr.sub.7 B.sub.3                                                    600       19200                                      ______________________________________                                         Heating rate: 160° C./m                                                Shape of sample: annular (inner diameter: 6 mm, outer diameter: 10 mm)        Measuring magnetic field: 5 mOe                                          

It is apparent from the results of the measurements shown in Tables 1 to5 and FIG. 1 that the magnetic permeabilities of the samples of the softmagnetic alloys considerably depend upon the heating rate at the time ofthe heat treatment and the magnetic permeability is raised substantiallyin proportion to the heating rate. A fact was found from the resultsshown in Tables 1 to 5 and FIG. 1 that the preferable heating rate(°C./minute) is 1.0 or higher to maintain the magnetic permeability at5000 or more.

Then, the actual magnetic permeability (μe) was measured in each exampleunder conditions of 5 mOe and 1 kHz. The coercive force (Hc) wasmeasured by a DC B-H loop tracer, and the saturation magnetic fluxdensity (Bs) was calculated in accordance with the magneticizationmeasured at 10 kOe with a VSM.

In the following Examples 2 to 6, the magnetic characteristics wereobtained by maintaining the temperature at 600° C. or 650° C. for onehour, followed by performing a water quenching. In Examples 7 to 17, themagnetic characteristics were obtained by maintaining the temperature at500° to 700° C. for one hour. The heating rate was set to 80° to 100°C./minute.

Example 2

The effect of the heat treatment acting on the magnetic characteristicsand the structure of a fourth aspect of the present invention will nowbe described in such a manner that a Fe₉₀ Zr₇ B₃ alloy which is one ofthe basic composition of the foregoing alloy is explained as an example.The temperature at which the crystallization of the Fe₉₀ Zr₇ B₃ alloyobtained from a differential thermal analysis at a heating rate of 10°C./minute was 480° C.

FIG. 2 illustrates an effect of annealing (maintained at eachtemperature for one hour) upon the effective magnetic permeability ofthe Fe₉₀ Zr₇ B₃ alloy. As can be understood from FIG. 2, the effectivemagnetic permeability becomes low in proportion to the annealingtemperature and it is rapidly increased by performing the annealing at500° to 650° C.

The dependency of the magnetic permeability upon the frequency of asample subjected to the heat treatment performed at 650° C. and having athickness of about 20 μm was examined, resulting in that excellent softmagnetic characteristics were attained even at high measuringfrequencies such that 26500 was attained at 1 KHz, 19800 was attained at10 KHz and 7800 was attained at 100 KHz.

Then, the change in the structure of the Fe₉₀ Zr₇ B₃ alloy subjected tothe heat treatment was examined by an X-ray analysis method, and thestructure formed after the heat treatment had been performed wasobserved by using a transmission electronic microscope. Results of theexamination is shown in FIGS. 3 and 4.

As can be understood from FIG. 3, a halo diffraction patterncorresponding to the amorphous was observed in a rapidly solidifiedstate, and a diffraction pattern corresponding to a body-centered cubicstructure was observed after the heat treatment had been performed.Therefore, it has been understood that the structure of the alloyaccording to the present invention has been changed from amorphous tothe body-centered cubic structure (bcc crystal). Further, another factcan be understood from the results of the observation of the structureshown in FIG. 4 that the structure realized after the heat treatment hadbeen performed was composed of fine crystal, the grain size of which wasabout 10 to 20 nm.

The change of the hardness of the Fe₉₀ Zr₇ B₃ alloy before and after theheat treatment was examined, resulting in that the Vickers hardness was,due to the heat treatment performed at 600° C., improved from 750 DPN inthe rapidly solidified state to 1400 DPN, which is excellent hardnessthat cannot be obtained from a conventional material. Therefore, theforegoing alloy is suitable as the material for the magnetic head.

As described above, the alloy according to this embodiment has astructure mainly composed of very small crystalline grains bycrystallizing the amorphous alloys having the foregoing compositions bythe heat treatment. Therefore, excellent characteristics can be attainedsuch that the saturation magnetic flux density is very high, excellentsoft magnetic characteristics, satisfactory hardness and excellent heatstability are attained.

Examples in which the quantities of Zr and B in the foregoing alloy arechanged will now be described. Tables 6 and FIGS. 5, 6, 7 and 8 show themagnetic characteristics realized after annealing has been performed.

                  TABLE 6                                                         ______________________________________                                                                             Saturation                                                                    Magnetic                                        Composition                                                                              Heat      Magnetic Flux                                     Sample of Alloy   Treatment Permeability                                                                           Density                                  No.    (atom %)   °C. 1h                                                                           μ (1 kHz)                                                                           Bs (G)                                   ______________________________________                                        85     Fe.sub.91 Zr.sub.8 B.sub.1                                                               600       12384    16700                                    86     Fe.sub.91 Zr.sub.9                                                                       600        1056    16500                                    87     Fe.sub.89 Zr.sub.9 B.sub.4                                                               600        1901    14900                                    88     Fe.sub.91 Zr.sub.5 B.sub.4                                                               600        3390    17300                                    89     Fe.sub.89 Zr.sub.5 B.sub.6                                                               600       24384    17000                                    90     Fe.sub.87 Zr.sub.5 B.sub.8                                                               600       10829    16000                                    91     Fe.sub.87 Zr.sub.3 B.sub.10                                                              600        296     17200                                    92     Fe.sub.87 B.sub.13                                                                       600        192     18000                                    93     Fe.sub.81 Zr.sub.7 B.sub.12                                                              600        230     12900                                    94     Fe.sub.85 Zr.sub.11 B.sub.4                                                              600         2       9000                                    95     Fe.sub.93 Zr.sub.7                                                                       600        4550    17300                                    96     Fe.sub.91 Zr.sub.7 B.sub.2                                                               600       24384    16600                                    97     Fe.sub.89 Zr.sub.7 B.sub.4                                                               600       20554    16000                                    98     Fe.sub.92 Zr.sub.7 B.sub.1                                                               600       17184    17100                                    99     Fe.sub.90 Zr.sub.7 B.sub.3                                                               600       23808    16600                                    100    Fe.sub.88 Zr.sub.7 B.sub.5                                                               600        8794    15500                                    101    Fe.sub.91 Zr.sub.7 B.sub.3                                                               600       19776    17100                                    102    Fe.sub.90 Zr.sub.6 B.sub.4                                                               600       22464    17000                                    103    Fe.sub.90 Zr.sub.8 B.sub.2                                                               600       10944    15900                                    104    Fe.sub.89 Zr.sub.8 B.sub.3                                                               600        8083    15400                                    ______________________________________                                         80° C./minute to 100° C./minute                                 Note) Sample Nos. 91, 92, 93, 94 and 95 are comparative examples.        

As can be understood from Table 6, and FIGS. 5, 6, 7 and 8, highmagnetic permeability and high saturation magnetic flux density caneasily be obtained if the quantity of Zr ranges from 4 to 9 atom %. Ifthe quantity of Zr is 4 atom % or less, an effective magneticpermeability higher than 10000 cannot be obtained. If the quantity islarger than 9 atom %, the magnetic permeability is rapidly lowered andthe saturation magnetic flux density is also lowered. Therefore, therange of the quantity of Zr in the alloy according to a fifth aspect ofthe present invention is made to be 4 to 9 atom %.

As for the quantity of B, a fact was found that high magneticpermeability of 5000 or more of an effective magnetic permeability,preferably 10000 or more, can easily be obtained in a range from 0.5atom % to 10 atom %. Therefore, the quantity of B is determined to be0.5 to 10 atom %. If the quantity of Fe is larger than 93 atom %, highmagnetic permeability cannot be obtained although the quantities of Zrand B are in the foregoing ranges. Therefore, the basic quantity of Feto be contained in the alloy according to the embodiment of the presentinvention is determined to be 93 atom %.

Example 3

A Fe--Hf--B alloy system obtained by substituting Zr of the Fe--Zr--Balloy system according to Example 2 by Hf will now be described.

Results of examples, in which the quantity of Hf in the Fe--Hf--B alloysystem was changed in a range from 4 to 9 atom %, are shown in Table 7.

                  TABLE 7                                                         ______________________________________                                                            Magnetic    Saturation                                    Sample Composition of                                                                             Permeability                                                                              Magnetic Flux                                 No.    Alloy (atom %)                                                                             μ (1 KHz)                                                                              Density Bs (G)                                ______________________________________                                        105    Fe.sub.88 Hf.sub.4 B.sub.8                                                                  8200       16200                                         106    Fe.sub.89 Hf5.sub.4 B.sub.6                                                                17200       16000                                         107    Fe.sub.90 Hf5.sub.6 B.sub.4                                                                24800       15500                                         108    Fe.sub.89 Hf5.sub.7 B.sub.4                                                                28000       15000                                         109    Fe.sub.88 Hf.sub.8 B.sub.4                                                                 25400       14500                                         110    Fe.sub.87 Hf.sub.9 B.sub.4                                                                 12100       14000                                         111    Fe.sub.91 Zr.sub.4 Hf.sub.3 B.sub.2                                                        27800       16500                                         ______________________________________                                    

As can be understood from Table 7, the effective magnetic permeabilityof the Fe--Hf--B alloy system is equivalent to that of the Fe--Zr--Balloy system if the quantity of Hf ranges from 4 to 9 atom %.

The magnetic characteristics of a Fe₉₁ Zr₄ Hf₃ B₂ alloy shown in Table 7are equivalent to those of the Fe--Zr--B alloy system according toExample 2. Therefore, it has been found that Zr in the Fe--Zr--B alloysystem according to Example 2 can be partially or fully substituted byHf in its composition range of 4 to 9 atom %.

Example 4

An example in which a portion of Zr and Hf in the Fe--(Zr, Hf)--B alloysystem according to Example 2 and Example 3 is substituted by Nb willnow be described.

Results of cases where a portion of Zr in the Fe--Zr--B alloy system issubstituted by 1 to 5 atom % Nb are shown in Table 8.

                  TABLE 8                                                         ______________________________________                                                            Magnetic    Saturation                                    Sample Composition of                                                                             Permeability                                                                              Magnetic Flux                                 No.    Alloy (atom %)                                                                             (1 KHz)     Density Bs (G)                                ______________________________________                                        112    Fe.sub.90 Zr.sub.6 Nb.sub.1 B.sub.3                                                        21000       16600                                         113    Fe.sub.89 Zr.sub.5 Nb.sub.2 B.sub.4                                                        14000       16200                                         114    Fe.sub.88 Zr.sub.6 Nb.sub.2 B.sub.4                                                        12500       15400                                         115    Fe.sub.87 Zr.sub.7 Nb.sub.2 B.sub.4                                                        7600        14500                                         116    Fe.sub.86 Zr.sub.8 Nb.sub.2 B.sub.4                                                        2300        14000                                         117    Fe.sub.89 Zr.sub.6 Nb.sub.3 B.sub.2                                                        8200        15900                                         118    Fe.sub.88 Zr.sub.6 Nb.sub.4 B.sub.2                                                        4100        14500                                         119    Fe.sub.87 Zr.sub.6 Nb.sub.5 B.sub.2                                                        1800        14000                                         120    Fe.sub.86 Ni.sub.1 Zr.sub.4 Nb.sub.3 B.sub.6                                               17900       15400                                         ______________________________________                                         Note) Sample Nos. 116, 118 and 119 are comparative examples.             

As can be understood from the results shown in Table 8, the quantity ofZr+Nb enabling a high magnetic permeability to be easily obtained is 4to 9 atom % which is the same as the case for Zr in the Fe--Zr--B alloysystem and Nb has an effect of addition which is similar to that of Zr.Therefore, a portion of Zr and that of Hf of the Fe--(Zr, Hf)--B alloysystem can be substituted by Nb.

Example 5

An example in which a portion of Nb in the Fe--(Zr, Hf)--Nb--B alloysystem according to Example 4 is substituted by Ti, V, Ta, Mo or W willnow be described.

As an example, the magnetic characteristics of a Fe--Zr--M'--B (where M'is an element selected from a group consisting of Ti, V, Ta, Mo and W)alloy system are shown in Table 9.

                  TABLE 9                                                         ______________________________________                                                            Magnetic    Saturation                                    Sample Composition of                                                                             Permeability                                                                              Magnetic Flux                                 No.    Alloy (atom %)                                                                             μ (1 KHz)                                                                              Density Bs (G)                                ______________________________________                                        121    Fe.sub.89 Zr.sub.6 Ti.sub.2 B.sub.3                                                        12800       15800                                         122    Fe.sub.89 Zr.sub.6 V.sub.2 B.sub.3                                                         11100       15800                                         123    Fe.sub.89 Zr.sub.6 Ta.sub.2 B.sub.3                                                        15600       15200                                         124    Fe.sub.89 Zr6.sub.7 Mo.sub.2 B.sub.3                                                       12800       15300                                         125    Fe.sub.89 Zr.sub.6 W.sub.2 B.sub.3                                                         13100       15100                                         126    Fe--Si--B     5000       14100                                                amorphous alloy                                                        127    Iron-Silicon  2400       18000                                                Steel                                                                         (Si: 6.5 wt %)                                                         128    Fe--Si--Al   20000       11000                                         129    Fe--Ni Alloy 15000        8000                                                (permalloy)                                                            130    Co--Fe--Si--B                                                                              65000        8000                                                amorphous alloy                                                        ______________________________________                                    

Each sample shown in Table 9 has excellent magnetic characteristicshaving an effective magnetic permeability superior to that of 5000 whichis usually obtained from a Fe-base amorphous alloy (sample No. 126) orthat of 2400 of Iron-silicon steel (sample No. 127) serving ascomparative examples. Further, saturation magnetic flux densitiessuperior to that of a Fe--Si--Al alloy (sample No. 128), that of aFe--Ni alloy (sample No. 129) and that of a Co-base amorphous alloy(sample No. 130). Therefore, a fact can be understood that the alloyaccording to this embodiment has high magnetic permeability and the highsaturation magnetic flux density superior to those of the alloysaccording to the comparative examples. Hence, Nb of Fe--(Zr, Hf)Nb--Balloy system can be substituted by Ti, V, Ta, Mo or W.

Example 6

The reason why the quantity of Co and that of Ni in the alloys accordingto a sixth aspect of the present invention are so determined will now bedescribed.

As an example, the relationship between the quantities of Co and Ni (a)of an alloy system (Z=Co, Ni), the composition of which is expressed by(Fe_(1-a) Za)₉₁ Zr₇ B₂ and the magnetic permeability is shown in FIG. 9.

As can be understood from results shown in FIG. 9, effectivepermeabilities of 5000 or more can be obtained, which are higher thanthat of the Fe amorphous alloy if the quantities of Co and Ni (a) are ina range of 0.1 or less. However, if the quantities are higher than 0.1,a practical problem arises because the effective magnetic permeabilitydeteriorates rapidly. Therefore, the quantities of Co and Ni (a) in thealloy according to the foregoing claims is determined to be 0.1 or less.Further, it is preferable that a 0.05 or less to obtain an effectivemagnetic permeability of 10000 or more.

Example 7

The effect of the heat treatment acting on the magnetic characteristicsand the structure claimed in according to a seventh aspect of thepresent invention will now be described in such a manner that a Fe₈₆ Zr₇B₆ Cu₁ alloy which is one of the basic composition of the foregoingalloy is explained as an example. The temperature at which thecrystallization of the Fe₈₆ Zr₇ B₆ Cu₁ alloy obtained from adifferential thermal analysis at a heating rate of 10° C./minute was503° C.

FIG. 10 illustrates an effect of annealing (maintained at eachtemperature for one hour) upon the effective magnetic permeability ofthe Fe₈₆ Zr₇ B₆ Cu₁ alloy.

As can be understood from the results shown in FIG. 10, the effectivemagnetic permeability of the alloy according to the present invention ina rapidly solidified state (RQ) is a low value equivalent to that of theFe-base amorphous alloy. However, the effective magnetic permeability isincreased to a value about 10 times the value in the rapidly solidifiedstate. The dependency of the magnetic permeability upon the frequencywas examined by using a sample having a thickness of about 20 μm andsubjected to heat treatment set to 600° C., resulting in that excellentsoft magnetic characteristics were attained even if the measuringfrequency was high, such that a magnetic permeability of 32000 wasobtained at 1 KHz, a magnetic permeability of 25600 was obtained at 10KHz and a magnetic permeability of 8330 was obtained at 100 KHz.

The magnetic characteristics of the alloy according to the presentinvention can be adjusted by adequately selecting the heat treatmentconditions, such as the heating rate. Further, the magneticcharacteristics can be improved by performing annealing or the like inthe magnetic field.

Then, the change in the structure of the Fe₈₆ Zr₇ B₆ Cu₁ alloy subjectedto the heat treatment was examined by an X-ray analysis method, and thestructure formed after the heat treatment had been performed wasobserved by using a transmission electronic microscope. Results of theexamination is shown in FIGS. 11 and 12.

As can be understood from FIG. 11, a halo diffraction patterncorresponding to the amorphous was observed in a rapidly solidifiedstate, and a diffraction pattern corresponding to a body-centered cubicstructure was observed after the heat treatment had been performed.Therefore, it has been understood that the structure of the alloysaccording to the present invention has been changed from amorphous tothe body-centered cubic structure.

FIG. 12 is a schematic view of a photograph of the transmissionelectronic microscope, from which the structure realized after the heattreatment had been performed was composed of fine grains, the grain sizeof which was about 10 nm.

The change of the hardness of the Fe₈₆ Zr₇ B₆ Cu₁ alloy before and afterthe heat treatment was examined, resulting in that the Vickers hardnesswas, due to the heat treatment performed at 650° C., improved from 740DPN in the rapidly solidified state to 1390 DPN, which is excellenthardness that cannot be obtained from a conventional material.Therefore, the foregoing alloy is suitable as the material for themagnetic head.

As described above, the alloys according to this embodiment has astructure mainly composed of very small grains by crystallizing theamorphous alloys having the foregoing composition by the heat treatment.Therefore, excellent characteristics can be attained such that thesaturation magnetic flux density is very high, excellent soft magneticcharacteristics, satisfactory hardness and excellent heat stability areattained.

Examples in which the quantities of Zr and B in the foregoing alloysaccording to the seventh aspect of the present invention will now bedescribed. Table 10 and FIG. 13 show the magnetic characteristicsrealized after annealing has been performed.

                  TABLE 10                                                        ______________________________________                                                                             Saturation                                                                    Magnetic                                        Composition Magnetic   Coercive                                                                             Flux                                     Sample of Alloy    Permeability                                                                             Force  Density                                  No.    (atom %)    μe (1k) Hc (Oe)                                                                              Bs (KG)                                  ______________________________________                                        131    Fe.sub.85 Zr.sub.4 B.sub.10 Cu.sub.1                                                       9250      0.150  14.9                                     132    Fe.sub.83 Zr.sub.4 B.sub.12 Cu.sub.1                                                       7800      0.170  14.2                                     133    Fe.sub.88 Zr.sub.5 B.sub.6 Cu.sub.1                                                       15500      0.190  16.7                                     134    Fe.sub.86 Zr.sub.5 B.sub.8 Cu.sub.1                                                       23200      0.032  15.2                                     135    Fe.sub.84 Zr.sub.5 B.sub.10 Cu.sub.1                                                      21100      0.055  14.5                                     136    Fe.sub.82 Zr.sub.5 B.sub.12 Cu.sub.1                                                      12000      0.136  13.9                                     137    Fe.sub.89 Zr.sub.6 B.sub.4 Cu.sub.1                                                       30300      0.038  17.0                                     138    Fe.sub.88 Zr.sub.6 B.sub.5 Cu.sub.1                                                       15200      0.052  16.3                                     139    Fe.sub.87 Zr.sub.6 B.sub.6 Cu.sub.1                                                       18300      0.040  15.7                                     140    Fe.sub.86 Zr.sub.6 B.sub.7 Cu.sub.1                                                       15400      0.042  15.2                                     141    Fe.sub.91 Zr.sub.7 B.sub.1 Cu.sub.1                                                       20700      0.089  17.1                                     142    Fe.sub.90 Zr.sub.7 B.sub.2 Cu.sub.1                                                       32200      0.030  16.8                                     143    Fe.sub.89 Zr.sub.7 B.sub.3 Cu.sub.1                                                       32400      0.036  16.2                                     144    Fe.sub.88 Zr.sub.7 B.sub.4 Cu.sub.1                                                       31300      0.102  15.8                                     145    Fe.sub.87 Zr.sub.7 B.sub.5 Cu.sub.1                                                       31000      0.082  15.3                                     146    Fe.sub.86 Zr.sub.7 B.sub.6 Cu.sub.1                                                       32000      0.044  15.0                                     147    Fe.sub.84 Zr.sub.7 B.sub.8 Cu.sub.1                                                       25700      0.044  14.2                                     148    Fe.sub.82 Zr.sub.7 B.sub.10 Cu.sub.1                                                      19200      0.038  13.3                                     149    Fe.sub.80 Zr.sub.7 B.sub.12 Cu.sub.1                                                      23800      0.044  12.5                                     150    Fe.sub.78 Zr.sub.7 B.sub.14 Cu.sub.1                                                      13300      0.068  11.8                                     151    Fe.sub.76 Zr.sub.7 B.sub.16 Cu.sub.1                                                      10000      0.20   11.0                                     152    Fe.sub.88 Zr.sub.8 B.sub.3 Cu.sub.1                                                       29800      0.084  15.4                                     153    Fe.sub.85 Zr.sub.8 B.sub.6 Cu.sub.1                                                       28000      0.050  14.2                                     154    Fe.sub.84 Zr.sub.8 B.sub.7 Cu.sub.1                                                       20400      0.044  13.8                                     155    Fe.sub.88 Zr.sub.9 B.sub.2 Cu.sub.1                                                       11700      0.112  15.1                                     156    Fe.sub.86 Zr.sub.9 B.sub.4 Cu.sub.1                                                       12900      0.160  14.3                                     157    Fe.sub.84 Zr.sub.9 B.sub.6 Cu.sub.1                                                       11800      0.108  13.1                                     158    Fe.sub.85 Zr.sub.10 B.sub.4 Cu.sub.1                                                       6240      0.210  12.8                                     159    Fe.sub.83 Zr.sub.10 B.sub.6 Cu.sub.1                                                       5820      0.220  12.0                                     ______________________________________                                    

As can be understood from Table 10, and FIG. 13, high magneticpermeability can easily be obtained if the quantity of Zr ranges from 4to 10 atom %. If the quantity of Zr is 4 atom % or less, an effectivemagnetic permeability of 5000 to 10000 or more cannot be obtained. Ifthe quantity is larger than 10 atom %, the magnetic permeability israpidly lowered and the saturation magnetic flux density is alsolowered. Therefore, the range of the quantity of Zr in the alloysaccording to the present invention is made to be 4 to 10 atom %.

As for the quantity of B, a fact was found that high magneticpermeability of 5000 or more of an effective magnetic permeability,preferably 10000 or more, can easily be obtained in a range from 0.5atom % to 18 atom %. Therefore, the quantity of B is determined to be0.5 to 18 atom %. If the quantity of Fe is larger than 93 atom %, highmagnetic permeability cannot be obtained although the quantities of Zrand B are in the foregoing ranges. Therefore, the basic quantity ofFe+Co to be contained in the alloys according to the seventh aspect isdetermined to be 93 atom %.

Example 8

A Fe--Hf--B--Cu alloy system obtained by substituting Zr of theFe--Zr--B--Cu alloy system according to Example 7 by Hf will now bedescribed.

Results of measurements of the magnetic characteristics of alloys eachhaving a constant composition that the quantity of B was 6 atom % andthat of Cu was 1 atom % are shown in Table 11. FIG. 14 shows thepermeabilities realized by changing the quantity of Hf in a range from 4to 10 atom %. FIG. 14 also shows an effective magnetic permeability ofthe Fe--Zr--B₆ --Cu₁ alloy system for comparison.

                  TABLE 11                                                        ______________________________________                                        Sam-                                Saturation                                ple  Composition of                                                                             Magnetic   Coercive                                                                             Magnetic                                  No.  Alloy        Permeability                                                                             Force  Flux Density                              ______________________________________                                        160  Fe.sub.89 Hf.sub.4 B.sub.6 Cu.sub.1                                                         9350      0.150  16.1                                      161  Fe.sub.88 Hf.sub.5 B.sub.6 Cu.sub.1                                                        20400      0.048  15.7                                      162  Fe.sub.87 Hf.sub.6 B.sub.6 Cu.sub.1                                                        26500      0.028  15.2                                      163  Fe.sub.86 Hf.sub.7 B.sub.6 Cu.sub.1                                                        25200      0.028  14.7                                      164  Fe.sub.85 Hf.sub.8 B.sub.8 Cu.sub.1                                                        25200      0.038  14.1                                      165  Fe.sub.84 Hf.sub.9 B.sub.6 Cu.sub.1                                                        19600      0.068  13.5                                      166  Fe.sub.83 Hf.sub.10 B.sub.6 Cu.sub.1                                                        9860      0.104  12.8                                      167  Fe.sub.86 Zr.sub.4 Hf.sub.3 B.sub.6 Cu.sub.1                                               39600      0.032  14.8                                      ______________________________________                                    

As can be understood from Table 11 and FIG. 14, the effective magneticpermeability of the Fe--Hf--B--Cu alloy system is equivalent to that ofthe Fe--Zr--B--Cu alloy system if the quantity of Hf ranges from 4 to 10atom %. The magnetic characteristics of a Fe₈₆ Zr₄ Hf₃ B₆ Cu₁ alloyshown in Table 11 are equivalent to those of the Fe--Zr--B--Cu alloysystem according to Example 7. Therefore, it has been found that Zr inthe Fe--Zr--B--Cu alloy system according to Example 7 can be partiallyor fully substituted by Hf in its composition range of 4 to 10 atom %.

Example 9

An example in which a portion of Zr and Hf in the Fe--(Zr, Hf)--B--Cualloy system according to Example 7 and Example 8 is substituted by Nbwill now be described.

Results of cases where a portion of Zr in the Fe--Zr--B--Cu alloy systemis substituted by 1 to 5 atom % Nb are shown in Table 12. FIG. 15 showsthe magnetic characteristics of the Fe--Zr--Nb--B--Cu alloy systemcontaining Nb by 3 atom %.

                  TABLE 12                                                        ______________________________________                                                                             Saturation                                                                    Magnetic                                      Composition   Magnetic   Coercive                                                                             Flux                                     Sam- of Alloy      permeability                                                                             Force  Density                                  ple  (atom %)      μe (1k) Hc (Oe)                                                                              Bs (KG)                                  ______________________________________                                        168  Fe.sub.88 Zr.sub.4 Nb.sub.1 B.sub.6 Cu.sub.1                                                11300      0.108  16.9                                     169  Fe.sub.87 Zr.sub.4 Nb.sub.2 B.sub.6 Cu.sub.1                                                37400      0.042  15.9                                     170  Fe.sub.86 Zr.sub.4 Nb.sub.3 B.sub.6 Cu.sub.1                                                35700      0.046  15.3                                     171  Fe.sub.85 Zr.sub.4 Nb.sub.4 B.sub.6 Cu.sub.1                                                30700      0.050  14.3                                     172  Fe.sub.84 Zr.sub.4 Nb.sub.5 B.sub.6 Cu.sub.1                                                14600      0.092  13.7                                     173  Fe.sub.86 Zr.sub.2 Nb.sub.3 B.sub.8 Cu.sub.1                                                14900      0.108  16.6                                     174  Fe.sub.84 Zr.sub.2 Nb.sub.3 B.sub.10 Cu.sub.1                                               15900      0.085  16.2                                     175  Fe.sub.87 Zr.sub.3 Nb.sub.3 B.sub.6 Cu.sub.1                                                33800      0.048  16.0                                     176  Fe.sub.85 Zr.sub.3 Nb.sub.3 B.sub.8 Cu.sub.1                                                24100      0.095  15.5                                     177  Fe.sub.88 Zr.sub.4 Nb.sub.3 B.sub.4 Cu.sub.1                                                16900      0.076  15.6                                     178  Fe.sub.84 Zr.sub.4 Nb.sub.3 B.sub.8 Cu.sub.1                                                38700      0.038  14.6                                     179  Fe.sub.86 Zr.sub.5 Nb.sub.3 B.sub.5 Cu.sub.1                                                24200      0.048  14.8                                     180  Fe.sub.84 Zr.sub.5 Nb.sub.3 B.sub.7 Cu.sub.1                                                21700      0.038  14.0                                     181  Fe.sub.84 Zr.sub.6 Nb.sub.3 B.sub.6 Cu.sub.1                                                17300      0.110  13.9                                     182  Fe.sub.82 Zr.sub.6 Nb.sub.3 B.sub.8 Cu.sub.1                                                20400      0.045  13.2                                     183  Fe.sub.79 Zr.sub.7 Nb.sub.3 B.sub.10 Cu.sub.1                                               10800      0.125  12.4                                     ______________________________________                                    

As can be understood from the results shown in Table 12 and FIG. 15, thequantity of Zr+Nb enabling a high magnetic permeability to be easilyobtained is 4 to 10 atom % which is the same as the case for Zr in theFe--Zr--B--Cu alloy system. In the foregoing range, a high effectivemagnetic permeability similarly to that of the Fe--Zr--B--Cu alloysystem was obtained. Therefore, a portion of Zr and that of Hf of theFe--(Zr, Hf)--B--Cu alloy system can be substituted by Nb.

Example 10

An example in which Nb in the Fe--(Zr, Hf)--Nb--B--Cu alloy systemaccording to Example 9 is substituted by Ti, V, Ta, Mo or W will now bedescribed. As an example, the magnetic characteristics of aFe--Zr--M'--B--Cu₁ (where M'=Ti, V, Ta, Mo or W) alloy system are shownin Table 13.

                  TABLE 13                                                        ______________________________________                                                                            Saturation                                     Composition  Magnetic   Coercive                                                                             Magnetic                                  Sam- of Alloy     permeability                                                                             Force  Flux Density                              ple  (atom %)     μe (1k) Hc (Oe)                                                                              Bs (KG)                                   ______________________________________                                        184  Fe.sub.80 Zr.sub.1 Ti.sub.6 B.sub.12 Cu.sub.1                                              13800      0.105  12.8                                      185  Fe.sub.86 Zr.sub.4 Ti.sub.3 B.sub.6 Cu.sub.1                                               12700      0.110  14.7                                      186  Fe.sub.84 Zr.sub.4 V.sub.5 B.sub.6 Cu.sub.1                                                6640       0.201  13.5                                      187  Fe.sub.86 Zr.sub.4 Ta.sub.3 B.sub.6 Cu.sub.1                                               20900      0.096  15.1                                      188  Fe.sub.84 Zr.sub.4 Ta.sub.5 B.sub.6 Cu.sub.1                                               8310       0.172  14.0                                      189  Fe.sub.86 Zr.sub.4 Mo.sub.3 B.sub.8 Cu.sub.1                                               9410       0.160  15.3                                      190  Fe.sub.84 Zr.sub.4 Mo.sub.5 B.sub.6 Cu.sub.1                                               9870       0.160  13.7                                      191  Fe.sub.86 Zr.sub.4 W.sub.3 B.sub.6 Cu.sub.1                                                1170       0.098  14.8                                      192  Fe.sub.84 Zr.sub.4 W.sub.5 B.sub.6 Cu.sub.1                                                6910       0.211  13.2                                      ______________________________________                                    

Each sample shown in Table 13 has excellent magnetic characteristicshaving an effective magnetic permeability superior to that of 5000 whichis usually obtained from a Fe-base amorphous alloy. Hence, Nb ofFe--(Zr, Hf)Nb--B--Cu alloy system can be substituted by Ti, V, Ta, Moor W.

Example 11

The reason why the quantity of Cu in the alloys according to the seventhaspect of the present invention are so determined will now be described.

As an example, the relationship between the quantities of Cu (z) of aFe_(87-x) Zr₄ Nb₃ B₆ Cu_(x) alloy system and the magnetic permeabilityis shown in FIG. 16.

As can be understood from FIG. 16, effective permeabilities of 10000 ormore can easily be obtained if z is in a range from 0.2 to 4.5 atom %.If z is 0.2 atom % or less, the effect of the addition of Cu cannoteasily be obtained. If z is larger than 4.5 atom %, the magneticpermeability deteriorates, resulting in a practical problem to occur. Ifz is 0.2 atom % or less, a practical effective magnetic permeability of5000 or more can be obtained but decrease in Cu raises the concentrationof Fe, causing the saturation magnetic flux density to be raised.Therefore, Cu may be added by a quantity larger than zero and as well asin a range of 0.2 atom % or less. As a result, the range of the contentof Cu in the alloys according to the present invention is determined tobe 4.5 atom %.

Example 12

An example in which Cu of each alloys according to Examples 7 to 11 issubstituted by Ag, Pd or Pt will now be described.

As an example, the magnetic characteristics of a Fe₈₆ Zr₄ Nb₃ B₆ T₁(T=Ag, Au, Pd or Pt) alloy system are shown in Table 14.

                  TABLE 14                                                        ______________________________________                                                                            Saturation                                Sam- Composition  Magnetic   Coercive                                                                             Magnetic                                  ple  of Alloy     Permeability                                                                             Force  Flux Density                              No.  (atom %)     μe (1k) Hc (Oe)                                                                              Bs (KG)                                   ______________________________________                                        193  Fe.sub.86 Zr.sub.4 Nb.sub.3 B.sub.6 Pd.sub.1                                               18800      0.064  15.4                                      194  Fe.sub.86 Zr.sub.4 Nb.sub.3 B.sub.6 Pt.sub.1                                               19900      0.096  14.8                                      195  Fe.sub.86 Zr.sub.4 Nb.sub.3 B.sub.6 Ag.sub.1                                               17800      0.090  15.3                                      196  Fe.sub.86 Zr.sub.4 Nb.sub.3 B.sub.6 Au.sub.1                                               21500      0.076  15.2                                      ______________________________________                                    

As can be understood from Table 14, each alloy has an excellenteffective magnetic permeability of 10000 or higher which issubstantially the same as that of Cu. Therefore, it can be understoodthat Cu in the alloys according to claims 11 and 15 can be substitutedby Ag, Au, Pd or Pt.

Example 13

The reason why the content of Co in the alloy according to an eighthaspect of the present invention is so determined will now be described.

As an example, the relationship between the quantity (a) of Co in a(Fe_(1-a) Co_(a))₈₆ Zr₄ Nb₃ B₆ Cu₁ alloy system and the magneticpermeability is shown in FIG. 17.

As can be seen from FIG. 17, an effective magnetic permeability of 5000or more, which is higher than that of a Fe amorphous alloy, is attainedif a ranges lower than 0.1. Therefore, the Co content (a) in the alloyaccording to claims 15 and 17 is determined to be 0.1 or less. In orderto attain a high effective magnetic permeability of 10000 or higher, itis preferable to make the Co content to be 0.05 or less.

Example 14

An example in which a thin film of the alloy according to a ninth aspectof the present invention was manufactured by a sputtering method willnow be described.

The thin film was manufactured in an Ar atmosphere by a high-frequencysputtering method. The thickness of the obtained film was 1 to 2 μm, thefilm being then subjected to a heat treatment set to 500° to 700° C. tomeasure the magnetic characteristics. Results of the magneticcharacteristics are shown in Table 15.

                  TABLE 15                                                        ______________________________________                                                                            Saturation                                Sam- Composition  Magnetic   Coercive                                                                             Magnetic                                  ple  of Alloy     Permeability                                                                             Force  Flux Density                              No.  (atom %)     μe (1k) Hc (Oe)                                                                              Bs (KG)                                   ______________________________________                                        197  Fe.sub.86 Zr.sub.7 B.sub.6 Cu.sub.1                                                        1900       0.31   15.0                                      198  Fe.sub.86 Zr.sub.4 Nb.sub.3 B.sub.6 Cu.sub.1                                               2050       0.30   15.2                                      199  Fe.sub.86 Hf.sub.7 B.sub.6 Cu.sub.1                                                        2020       0.28   14.7                                      200  Fe--Al--Si   3000       0.30   10.0                                      ______________________________________                                    

As can be understood from Table 15, any alloy films according to thepresent invention has excellent soft magnetic characteristics. Further,the alloys according to the present invention can be manufactured by thesputtering method. It should be noted that Table 15 also shows thecharacteristics of a Fe--Al--Si alloy film (sample No. 200) as acomparative example. In contrast with the alloy films according to thecomparative example, the alloy films according to the present inventionexhibiting considerably superior saturation magnetic flux densityalthough the magnetic permeability is somewhat inferior.

Example 15

The effect of the heat treatment acting on the magnetic characteristicsand the structure of the alloys having the composition according to atenth aspect of the present invention will now be described in such amanner that a Fe₈₀ Nb₇ B₁₂ Cu₁ alloy which is one of the basiccomposition of the alloys having the compositions according to the tenthaspect is explained as an example. The temperature at which thecrystallization of the Fe₈₀ Nb₇ B₁₂ Cu₁ alloy obtained from adifferential thermal analysis at a heating rate of 10° C./minute was470° C. In this case, the addition of Nb is needed, and a portion of itmay be substituted by Ti or Ta to obtain similar magneticcharacteristics.

FIG. 18 illustrates an effect of annealing (maintained at eachtemperature for one hour) upon the effective magnetic permeability ofthe Fe₈₀ Nb₇ B₁₂ Cu₁ alloy.

As can be understood from FIG. 18, the effective magnetic permeabilityof the alloy according to the present invention in a rapidly solidifiedstate (RQ) is a low value equivalent to that of the Fe-base amorphousalloy. However, the effective magnetic permeability is increased to avalue about 10 times the value in the rapidly solidified state. Thedependency of the magnetic permeability upon the frequency was examinedby using a sample having a thickness of about 20 μm and subjected toheat treatment set to 600° C., resulting in that excellent soft magneticcharacteristics were attained even if the measuring frequency was high,such that a magnetic permeability of 28800 was obtained at 1 KHz, amagnetic permeability of 25400 was obtained at 10 KHz and a magneticpermeability of 7600 was obtained at 100 KHz.

FIG. 19 shows the results of influences of the content of B upon theeffective magnetic permeability of the alloys, the composition of whichis expressed by Fe_(92-x) Nb₇ B_(x) Cu₁. FIG. 19 shows the results ofthe measurements of the magnetic permeability performed byincreasing/decreasing the content of B in a range from 6 to 18%.

A fact shown in FIG. 19 was found that excellent magnetic permeabilitycan be obtained if the content of B ranges from 6.5 to 18 atom %.Therefore, the content of B in the alloys according to the tenth aspectis determined to be 6.5 to 18%.

Example 16

FIG. 20 shows results of influences of the content of Nb upon theeffective magnetic permeability of the alloys, the composition of whichis expressed by Fe_(87-x) Nb_(x) B₁₂ Cu₁. The results shown in FIG. 20were obtained by increasing/decreasing the content of Nb in a range from3 to 11 atom %.

As can be seen the results shown in FIG. 20, it was found that excellentmagnetic permeability can be obtained if Nb is contained by a quantityranging from 4 to 10 atom %. Therefore, the content of Nb according tothe tenth aspect is determined to be 4 to 10%.

Then, the change in the structure of the Fe_(87-x) Nb_(x) B₁₂ Cu₁ alloysubjected to the heat treatment was examined by an X-ray analysismethod, and the structure formed after the heat treatment had beenperformed was observed by using a transmission electronic microscope.Results of the examination is shown in FIGS. 21 and 22.

As can be understood from FIG. 21, a halo diffraction patterncorresponding to the amorphous was observed in a rapidly solidifiedstate, and a diffraction pattern corresponding to a crystallinestructure was observed after the heat treatment had been performed.Therefore, it has been understood that the structure of the alloysaccording to the present invention has been changed from amorphous tothe crystalline structure.

Further, another fact can be understood from FIG. 22 that the structurerealized after the heat treatment had been performed was composed offine crystal, the grain size of which was about 10 nm.

The change of the hardness of the Fe_(87-x) Nb_(x) B₁₂ Cu₁ alloy systembefore and after the heat treatment was examined, resulting in that theVickers hardness was, due to the heat treatment performed at 600° C.,improved from 650 DPN in the rapidly solidified state to 950 DPN.Therefore, the foregoing alloy is suitable as the material for themagnetic head.

As described above, the alloys according to the tenth aspect has astructure mainly composed of very small crystalline grains bycrystallizing the amorphous alloy having the foregoing composition bythe heat treatment. Therefore, excellent characteristics can be attainedsuch that the saturation magnetic flux density is very high, excellentsoft magnetic characteristics, satisfactory hardness and excellent heatstability are attained. Further, the elements mainly used in the alloysaccording to the present invention has a restricted tendency ofgenerating an oxide and, accordingly, the alloys can easily bemanufactured because it cannot easily be oxidized. The temperature, atwhich the heat treatment is performed, must be determined depending uponthe composition, the temperature being ranged from 400° to 750° C.

An example in which the quantity Fe+Cu, the quantity of B and that of Nbrespectively are increased/decreased in the basic composition of thesoft magnetic alloys according to the tenth aspect of the presentinvention to measure the change in the magnetic permeability. Results ofthe measurements are shown in FIG. 23.

As can be seen from FIG. 23, a range with which an excellent magneticpermeability of about 10000 is attained when the quantity of Nb rangesfrom 4 to 10 atom %. As for the quantity of B, the excellent magneticpermeability is attained when it ranges from 6.5 to 18 atom %.

An example in which the quantity Fe+Cu, the quantity of B and that of Nbrespectively are increased/decreased in the basic composition of thesoft magnetic alloys according to the tenth aspect of the presentinvention to measure the change in the saturation magnetic flux density.Results of the measurements are shown in FIG. 24.

As can be seen from FIG. 24, excellent values of 13 kG to 16 kG can beobtained in the range of the composition of the alloys according to thepresent invention.

The reason why the quantity of Cu in the alloys having the compositionsaccording to the tenth aspect is so determined will now be described.

As an example, the relationship between the Cu quantity (z) in aFe₈₂.5-z Nb₇ B₁₀.5 Cu_(z) alloy system and the magnetic permeability isshown in FIG. 25.

As can be understood from FIG. 25, effective permeabilities can easilybe obtained if the quantity of Cu is in a range from 0.2 to 4.5 atom %.If the quantity of Cu is 0.2 atom % or less, the effect of the additionof Cu cannot easily be obtained. If the quantity of Cu is larger than4.5 atom %, the magnetic permeability deteriorates, resulting in apractical problem to occur. If the quantity of Cu is 0.2 atom % or less,a practical effective magnetic permeability of 5000 or more can beobtained and the saturation magnetic flux density can be somewhatraised. Therefore, Cu may be added by a quantity of 0.2 atom % or less.As a result, the range of the content of Cu in the alloys according tothe present invention is determined to be 4.5 atom % or less.

A Fe--Nb--Ta--B--Cu alloy system, a Fe--Nb--Ti--B--Cu alloy system andFe--Nb--Ta--Ti--B--Cu alloy system obtained by substituting Nb of theforegoing Fe--Nb--B--Cu alloy system by a plurality of elements will nowbe described.

As examples, FIG. 26 shows the permeabilities of alloys realized whenthe quantities are increased/decreased in a range from 4 to 10 atom % ina case where the quantities of B and Cu respectively are made to beconstant values of 12 atom % and 1% and Nb and a portion of Nb aresubstituted by Ta and Ti.

As can be understood from FIG. 26, a similar magnetic permeability wasobtained from the alloys having the foregoing compositions.

Further, the saturation magnetic flux density (kG) of the alloys havingthe compositions shown in Table 16 was measured.

                  TABLE 16                                                        ______________________________________                                        Composition of  Saturation Magnetic                                           Alloy           Flux Density  μe (1 kHz)                                   ______________________________________                                        Fe.sub.84 Nb.sub.7 B.sub.8 Cu.sub.1                                                           15.3    (kG)      31000                                       Fe.sub.80 Ta.sub.7 B.sub.12 Cu.sub.1                                                          12.0              20000                                       Fe.sub.82 Ti.sub.7 B.sub.10 Cu.sub.1                                                          14.0              26000                                       Fe.sub.82 Ta.sub.4 Ti.sub.3 B.sub.10 Cu.sub.1                                                 14.0              24000                                       Fe.sub.82 Nb.sub.3 Ta.sub.2 Ti.sub.2 B.sub.10 Cu.sub.1                                        14.1              20000                                       ______________________________________                                    

As a result, it can be found that Nb of the Fe--Nb--B--Cu alloy systemcan be substituted by Ta and/or Ti, and Nb can be substituted by Nb andTi, Nb can be substituted by Ta and Ti, and Nb can be substituted by Taand Ti.

As can be understood from the explanation of the foregoing examples, thesoft magnetic alloys having the composition according to the tenthaspect is an excellent material having a high magnetic permeability of10000 or higher, an excellent saturation magnetic flux density of 12 to15.3 kG, excellent heat resistance and satisfactory hardness.

Therefore, the soft magnetic alloys according to the present inventionis a material suitable to be used in a magnetic head, a transformer or achoke coil, resulting in effects to be obtained with the foregoing unitsthat the performance can be improved and the size and the weight can bereduced.

Example 17

The effect of the heat treatment acting on the magnetic characteristicsand the structure of the alloys according to an eleventh aspect of thepresent invention will now be described in such a manner that a Fe₈₄ Nb₇B₉ alloy which is one of the basic composition of the foregoing alloy isexplained as an example. The temperature at which the crystallization ofthe foregoing alloy obtained from a differential thermal analysis at aheating rate of 10° C./minute was 490° C.

FIG. 27 illustrates an effect of annealing (maintained at eachtemperature for one hour) upon the effective magnetic permeability (me)and the saturation magnetic flux density (Bs) of the foregoing alloy.

As can be understood from the results shown in FIG. 27, the effectivemagnetic permeability of the alloy according to the present invention ina rapidly solidified state (RQ) is a low value. However, the effectivemagnetic permeability is rapidly increased due to annealing set to 550°to 680° C. The dependency of the magnetic permeability upon thefrequency was examined by using a sample having a thickness of about 20μm and subjected to heat treatment set to 650° C., resulting in thatexcellent soft magnetic characteristics were attained even if themeasuring frequency was high, such that a magnetic permeability of 22000was obtained at 1 KHz, a magnetic permeability of 19000 was obtained at10 KHz and a magnetic permeability of 8000 was obtained at 100 KHz. Themagnetic characteristics of the alloys according to the presentinvention can be adjusted by adequately selecting the heat treatmentconditions, such as the heating rate. Further, the magneticcharacteristics can be improved by performing annealing or the like inthe magnetic field.

FIG. 28 shows results of influences of the content of B upon theeffective magnetic permeability of the alloy, the composition of whichis expressed by Fe_(93-x) Nb₇ B_(x) and Fe_(92-x) Nb₆ B_(x). The resultsshown in FIG. 28 were obtained by increasing/decreasing the content of Bin a range from 6 to 10 atom % and 8 to 14 atom % for Fe_(93-x) Nb₇B_(x) and Fe_(92-x) Nb₆ B_(x), respectively.

As can be seen the results shown in FIG. 28, it was found that excellentmagnetic permeability can be obtained if B is contained by a quantityranging from 6.5 to 14 atom %. Therefore, the content of B according tothe eleventh aspect is determined to be 6.5 to 14%.

Then, the change in the structure of the Fe_(93-x) Nb₇ B_(x) alloysystem subjected to the heat treatment was examined by an X-ray analysismethod, and the structure formed after the heat treatment had beenperformed was observed by using a transmission electronic microscope.Results of the examination is shown in FIGS. 29 and 30.

As can be understood from FIG. 30, a halo diffraction patterncorresponding to the amorphous was observed in a rapidly solidifiedstate, and a diffraction pattern corresponding to a crystallinestructure was observed after the heat treatment had been performed.Therefore, it has been understood that the structure of the alloysaccording to the present invention has been changed from amorphous tothe crystalline structure.

Further, another fact can be understood from FIG. 30 that the structurerealized after the heat treatment had been performed was composed offine grains, the grain size of which was about 10 to 20 nm.

The change of the hardness of the Fe₈₄ Nb₇ B₉ alloy before and after theheat treatment was examined, resulting in that the Vickers hardness was,due to the heat treatment set to 650° C., improved from 650 DPN in therapidly solidified state to 950 DPN. Therefore, the foregoing alloy issuitable as the material for the magnetic head.

As described above, the alloys according to the eleventh aspect has astructure mainly composed of very small crystalline grains bycrystallizing the amorphous alloy having the foregoing composition bythe heat treatment. Therefore, excellent characteristics can be attainedsuch that the saturation magnetic flux density is very high, excellentsoft magnetic characteristics, satisfactory hardness and excellent heatstability are attained. Further, the elements mainly used in the alloysaccording to the present invention has a restricted tendency ofgenerating an oxide and, accordingly, the alloys can easily bemanufactured because it cannot easily be oxidized.

An example in which the quantity of Fe, the quantity of B and that of Nbrespectively are increased/decreased in the basic composition of thesoft magnetic alloys according to the present invention to measure thechange in the magnetic permeability. Results of the measurements areshown in FIG. 33.

As can be seen from FIG. 31, the composition of the alloys according tothe present invention enables an excellent value to 13 kG to 15 kG to beobtained.

The reason why the quantities of Co and Ni in the alloys according tothe eleventh aspect of the present invention are so determined will nowbe described.

As an example, the relationship between the quantity of Co and the Niquantity (a) in a (Fe_(1-a) Z_(a))₈₄ Nb₇ B₉ alloy system and themagnetic permeability is shown in FIG. 32.

As can be understood from FIG. 32, an excellent magnetic permeabilityequivalent to that of the Fe amorphous alloy can be obtained if thequantity of Co and the Ni quantity (a) are in a range of 0.1 or lower.If the quantities are larger than 0.1, the magnetic permeability rapidlyundesirably deteriorates. Therefore, the quantities of Co and Ni aredetermined to be 0.1 or less in the present invention.

Table 17 shows results of measurements of the magnetic characteristicsof soft magnetic alloys obtained by subjecting Fe--Nb--Ta--B--Cu alloysystem, a Fe--Nb--Ti--B alloy system and Fe--Nb--Ta--Ti--B alloy systemobtained by substituting Nb of the foregoing Fe--Nb--B alloy by aplurality of elements to heat treatment at a heating rate of 80° to 100°C./minute.

                  TABLE 17                                                        ______________________________________                                        Composition      μe (1 kHz)                                                                           Bs (kG)                                            ______________________________________                                        Fe.sub.84 Nb.sub.7 B.sub.9                                                                     23500     15.3                                               Fe.sub.84 Nb.sub.4 Ta.sub.2 Ti.sub.1 B.sub.9                                                   12000     15.0                                               Fe.sub.84 Nb.sub.6 Ti.sub.1 B.sub.9                                                            12500     15.0                                               Fe.sub.84 Nb.sub.6 Ta.sub.1 B.sub.9                                                            11000     14.9                                               ______________________________________                                    

As can be understood from the results shown in Table 17, the foregoingalloys enabled similar magnetic permeability and saturation magneticflux density to be obtained.

As a result, it can be found that Nb of the Fe--Nb--B alloy system canbe substituted by Ta and/or Ti, and Nb can be substituted by Nb and Ti,Nb can be substituted by Nb and Ti, and Nb can be substituted by Nb, Taand Ti.

As can be understood from the explanation of the foregoing examples, thesoft magnetic alloys having the composition according to the eleventhaspect is an excellent material having a high magnetic permeabilityequivalent to or superior to that of the Fe amorphous alloy, anexcellent saturation magnetic flux density of about 15 kG, excellentheat resistance and satisfactory hardness.

Therefore, the soft magnetic alloys according to the eleventh aspect ofthe present invention is a material suitable to be used in a magnetichead, a transformer or a choke coil, resulting in effects to be obtainedwith the foregoing units that the performance can be improved and thesize and the weight can be reduced.

Example 18

FIGS. 33 (a), (b) and (c) show the relationship among measured magneticpermeability (μe), the magnetostriction (λs) and the saturation magneticflux density (Bs) while changing the quantity of Co in samples havingcompositions (Fe_(1-x) Co_(x))₉₀ Zr₇ B₃. The foregoing measurements wereperformed under similar conditions according to the foregoing examples.

As can be seen from the results shown in FIG. 33, a magneticpermeability of 20000 or higher can be obtained if the Co quantity (a)ranges from 0.01 to 0.03. As for the saturation magnetic flux density,an excellent value of 16.4 kG to 17 kG is attained even if the Coquantity is changed. Another fact was found that, since themagnetostriction varies in a range from -1×10⁻⁶ to +3×10⁻⁶ in accordancewith the change of the Co quantity, the magnetostriction can be adjustedby substituting a portion of Fe by Co and by selecting an adequatecomposition. Therefore, the magnetostriction can be adjusted whileconsidering the influence of the pressure applied at the time of moldingthe resin upon the magnetostriction.

Example 19

FIG. 34 shows results of measurements of the core loss of an alloyhaving the composition expressed by Fe₈₉ Hf₇ B₄ according to the presentinvention and that of a Fe--Si--B amorphous alloy according to acomparative example. The core loss was measured under conditions thatannular samples were manufactured, a coil is fastened around eachsample, a sine wave electric current is applied, and a Sin B-mode wasemployed in which Fourier transformation is performed to calculatenumerals.

As can be seen from results shown in FIG. 34, the alloys having thecomposition according to the present invention displayed reduced coreloss as compared with the amorphous alloy according to the comparativeexample at each of frequencies 50 Hz, 400 Hz, 1 kHz, 10 kHz and 50 kHz.

Example 20

Samples of alloys having the compositions according to the presentinvention were manufactured to measure the relationship between theheating rate at the time of manufacturing the samples and the magneticpermeability of the manufactured samples, resulting in as shown in FIGS.35 to 38.

FIG. 35 shows, by plotting, the relationship between the heating rateand the magnetic permeability of plural samples selected from among thesamples the compositions of which are shown in Table 2. FIG. 36 showsresults of similar measurements obtained by using the samples shown inTable 3. FIG. 37 shows results of similar measurements obtained by usingthe samples shown in Table 4. FIG. 38 shows results of similarmeasurements obtained by using the samples shown in Table 5.

As can be seen from results shown in FIGS. 35 to 38, each of the alloyshaving the compositions according to the present invention has atendency of improving the magnetic permeability when the heating rate isimproved.

Example 21

FIG. 39 shows the relationship between the average grain size of thecrystal and the coercive force of the samples having the compositionsshown in the following Table 18.

                  TABLE 18                                                        ______________________________________                                                     Average Crystalline                                                                          Coercive Force                                    Composition  Grain Size (nm)                                                                              (Oe)                                              ______________________________________                                        Fe.sub.84 Nb.sub.7 B.sub.9                                                                 10             0.1                                               Fe.sub.86 Zr.sub.7 B.sub.6 Cu.sub.1                                                        10             0.03                                              Fe.sub.89 Hf.sub.7 B.sub.4                                                                 15             0.07                                              (Fe.sub.0.99 Co.sub.0.01).sub.90 Zr.sub.7 B.sub.3                                          15             0.07                                              Fe.sub.91 Zr.sub.7 B.sub.2                                                                 18             0.09                                              Fe.sub.86 B.sub.14                                                                           28.8         4.0                                               Fe.sub.79 Cr.sub.7 B.sub.14                                                                  37.2         15.0                                              Fe.sub.79 V.sub.7 B.sub.14                                                                   46.9         13.8                                              Fe.sub.83 W.sub.7 B.sub.10                                                                   87.2         14.9                                              ______________________________________                                    

As can be seen from Table 18, excellent coercive force can be obtainedby making the average grain size of crystal to be 30 nm or less.

As a result, the inventors of the present invention have attempted toimprove the magnetic characteristics by forming a finer structure byimproving the heat treatment process to which the alloy is subjected.While considering the theory of crystallization of the amorphous alloy(theory of nucleation and growth), a small grain size can be obtained ifconditions are satisfied with which a high nuclei generation speed and alow growth speed are obtained. In usual, the nuclei generation speed andthe growth speed are the functions of the temperature, and the foregoingconditions have been considered that the conditions can be met bylengthening the heat treatment period in a low temperature region.However, the inventors of the present invention considered that theheating rate is raised on the contrary to the foregoing conventionalconcept as a result of the following examples.

Example 22

FIG. 40 shows the relationship between the measured time t and thefraction transformed (crystal volume fraction) realized whencrystallization is performed at a constant temperature by using asample, the composition of which is expressed by Fe₉₀ Zr₇ B₃. The time tshown by the axis of abscissa of FIG. 40 will now be described. It hasbeen known that the volume fraction of the crystal x and the time t holdthe relationship expressed by an equation known as a JMA(Johnson-Mehl-Avrami)'s equation:

    x=1-exp (-kt.sup.n)

where exponent n is a parameter varying depending upon the crystaldeposition mechanism.

In accordance with the foregoing relationship, the logarithm of thecrystallization fraction shown in FIG. 40 is taken and plotted as shownin FIG. 41. The operation for obtaining the illustrated relationship isusually called "JMA plotting".

If spherical deposition is generated uniformly, it has been known thatthe value of n is 1.5 to 3. If crystallization takes place at 490° C. orhigher in the case shown in FIG. 41, the value of n is 1.9 to 2.2,resulting in that substantially uniform bcc (body centered cubic)crystal is precipitated. At a low temperature of 450° C., the value of nis 1.0 and a fact is shown that the state of the precipitation of thebcc crystal is nonuniform. As a result, a fact can be understood thatthe crystallization performed at a higher temperature is effective toobtain a uniform and precise structure. Since the crystallizationtemperature of amorphous is usually raised in proportion to the heatingrate, uniform fining of the structure is expected by raising the heatingrate.

FIG. 42 shows the results of measurements of the grain size of thecrystal of the sample of the alloy having a composition expressed byFe₉₀ Zr₇ B₃ obtained by raising the heating rate α=200° C./minute underthe conditions according to the present invention. FIG. 43 shows resultsof measurements of the grain size of the crystal of the sample of thealloy having the same composition obtained by raising the temperature ata heating rate α=2.5° C./minute.

As can be seen from the results of the measurements of the grain sizedistribution of bcc crystal, the sample, the temperature of which wasraised at a condition α=200° C./minute, has a small average grain sizewhile realizing a sharp grain size distribution and concentrated grainsize distribution in a small region. In contrast with this, the sample,the temperature of which is raised at a heating rate of 2.5° C./minutehas a large average grain size and displays a broad grain sizedistribution.

As can be understood from the above explanation, the average grain sizeof crystal can be reduced by raising the heating rate on the contrary tothe conventional wisdom.

Example 23

FIGS. 44 and 45 show results of examinations of structures by using atransmission electronic microscope to examine the grain size of crystalof the alloy, structure of which is expressed by Fe₉₀ Zr₇ B₃.

Since the structure was observed by looking the dark visual field, onlyspecific crystal grains are shown. However, the actual structure isoccupied with similar crystal grains.

As can be understood from FIGS. 44 and 45, a fact was easily confirmedthat the alloy according to the present invention has a finer structurein the case where the heating rate was raised.

Example 24

Samples having the compositions shown in the following Table 19 weremanufactured and the corrosion resistance of the samples were tested.The corrosion resistance was measured under conditions of 40° to 60° C.,95% RH and 96 hours. In table 19, samples having no rust were indicatedwith O, samples having rust for 1% or less of the overall area wereindicated with Δ and samples having rust over 1% of the overall areawere indicated with x.

                  TABLE 19                                                        ______________________________________                                                       Magnetic                                                       Composition    Permeability                                                                              State of Corrosion                                 ______________________________________                                        Fe.sub.89 Zr.sub.7 B.sub.3 Ru.sub.1                                                          19800       Δ                                            Fe.sub.82.5 Zr.sub.4 Nb.sub.3 B.sub.6.5 Cu.sub.1 Ru.sub.3                                    24000       ∘                                      Fe.sub.84.5 Zr.sub.7 B.sub.5 Cu.sub.1 Cr.sub.0.5 Ru.sub.2                                    28000       ∘                                      Fe.sub.85 Zr.sub.3.5 Nb.sub.3.5 B.sub.7 Cu.sub.1                                             32000       X                                                  (Comparative example)                                                         Fe.sub.80 Zr.sub.7 B.sub.6 Cu.sub.1 Cr.sub.6                                                  800        ∘                                      (Comparative example)                                                         ______________________________________                                    

As can be understood from Table 19, it was found that the samples havingthe compositions according to the present invention exhibit excellentcorrosion resistance. A fact was found from the results of theexperiments, the corrosion resistance of the alloys having thecomposition according to the present invention can be improved whilemaintaining realized magnetic characteristics by adding Ru and Cr by 5atom % or less.

Example 25

Samples of amorphous alloys having compositions shown in the followingTable 20 were manufactured and the core loss, the magnetostriction (λs)and the specific resistance (ρ) of the samples were measured, resultingin as shown in the table. The thickness (t) of each sample is shown inTable 20. The samples according to the present invention were measuredunder conditions that: the heating rate was 80° to 100° C./minute andthe heat treatment temperature was 650° C. However, the Fe--Si--Bamorphous alloy was subjected to heat treatment set to 370° C.

                  TABLE 20                                                        ______________________________________                                                                             Fe--Si--B                                                                     amorphous                                         Fe.sub.90 Zr.sub.7 B.sub.3                                                              Fe.sub.89 Hf.sub.7 B.sub.4                                                              Fe.sub.84 Nb.sub.7 B.sub.9                                                            alloy                                    Structure                                                                              bcc       bcc       bcc     amorphous                                ______________________________________                                        .sup.w 14/50.sup.a                                                                     0.21      0.14      0.19    0.24                                     (w/kg)                                                                        .sup.w 10/400.sup.a                                                                    0.82      0.61      0.97    1.22                                     (w/kg)                                                                        .sup.w 10/1k.sup.a                                                                     2.27      1.70      2.50    3.72                                     (w/kg)                                                                        .sup.w 2/100k.sup.a                                                                    79.7      59.0      75.7    168                                      (w/kg)                                                                        λs × 10.sup.6                                                             -1.1      -1.2      0.1     27                                       p × 10.sup.8 (Ωm)                                                          44        48        58      137                                      t (μm)                                                                              18        17        22      20                                       ______________________________________                                         a .sup.w α/β: core loss (α × 10.sup.-1 T and .beta     Hz.)                                                                          b f = 1 kHz; Hm = 5 mOe                                                  

As can be understood from Table 20, the samples of the alloys accordingto the present invention has a core loss lower than that of theFe--Si--B amorphous alloy according to the comparative example and alsohas a reduced magnetostriction.

As described above, the manufacturing method according to the presentinvention is able to manufacture the Fe-base soft magnetic alloys havingsoft magnetic characteristics equivalent to or superior to those of theconventional practical alloy, superior magnetic permeability andsaturation magnetic flux density. Further, the soft magnetic alloysaccording to the present invention has excellent mechanical strength andsatisfactory heat stability.

By performing the heat treatment set at the heating rate of 1.0°C./minute or higher, the magnetic permeability can stably be improved.

Since Nb and Ta which are elements to be added to the alloys accordingto the present invention are thermally stable elements, the fear ofdenaturing due to the oxidation or reduction reaction at the time of themanufacturing process can be eliminated. Therefore, an advantage can berealized that the manufacturing conditions can be made easy.

As a result, the Fe-base soft magnetic alloys obtained by the methodaccording to the present invention can be suitably used in a magnetichead which must be adapted to the trend of enlarging the coercive forceof a magnetic recording medium, and a transformer and a choke coil eachof which is required to have a smaller size. If the present invention isadapted to the foregoing purpose, the performance of the foregoing unitscan be improved and the size and the weight of the same can be reduced.

Although the invention has been described in its preferred form with acertain degree of particularly, it is understood that the presentdisclosure of the preferred form has been changed in the details ofconstruction and the combination and arrangement of parts may beresorted to without departing from the spirit and the scope of theinvention as hereinafter claimed.

What is claimed is:
 1. A method of manufacturing a Fe-base soft magneticalloy comprising a step of:forming an amorphous alloy ribbon mainlycomposed of Fe; subjecting the amorphous alloy ribbon to heat treatmentin which said amorphous alloy ribbon is heated at a heating rate of 10°C./minute or higher so that at least 50% or more of the structure ofsaid amorphous alloy ribbon is made of fine crystalline grains formedinto a body-centered cubic structure and having an average grain size ofcrystal of 30 nm or smaller.
 2. A method of manufacturing a Fe-base softmagnetic alloy according to claim 1, wherein said heat treatment is soarranged that said heating at said heating rate is performed and thenthe temperature is maintained at 400° to 750° C.
 3. A method ofmanufacturing a Fe-base soft magnetic alloy according to claim 2,wherein said Fe-base soft magnetic alloy is composed as expressed by thefollowing formula:

    Fe.sub.b B.sub.x M.sub.y

where M is one or more elements selected from a group consisting of Ti,Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf, 75≦b≦93 atom %,0.5≦x≦10 atom % and 4≦y≦9 atom %.
 4. A method of manufacturing a Fe-basesoft magnetic alloy according to claim 2, wherein said Fe-base softmagnetic alloy is composed as expressed by the following formula:

    Fe.sub.b B.sub.x M.sub.y X.sub.u

where M is one or more elements selected from a group consisting of Ti,Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf, X is one or moreelements selected from a group consisting of Cr, Ru, Rh and Ir, 75≦b≦93atom %, 0.5≦x≦10 atom %, 4≦y≦9 atom % and u≦5 atom %.
 5. A method ofmanufacturing a Fe-base soft magnetic alloy according to claim 2,wherein said Fe-base soft magnetic alloy is composed as expressed by thefollowing formula:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M.sub.y

where Z is Co and/or Ni, M is one or more elements selected from a groupconsisting of Ti, Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf,a≦0.1, 75≦b≦93 atom %, 0.5≦x≦10 atom % and 4≦y≦9 atom %.
 6. A method ofmanufacturing a Fe-base soft magnetic alloy according to claim 2,wherein said Fe-base soft magnetic alloy is composed as expressed by thefollowing formula:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M.sub.y X.sub.u

where Z is Co and/or Ni, M is one or more elements selected from a groupconsisting of Ti, Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf,X is one or more elements selected from a group consisting of Cr, Ru, Rhand Ir, a≦0.1, 75≦b≦93 atom %, 0.5≦x≦10 atom %, 4≦y≦9 atom % and u≦5atom %.
 7. A method of manufacturing a Fe-base soft magnetic alloyaccording to claim 2, wherein said Fe-base soft magnetic alloy iscomposed as expressed by the following formula:

    Fe.sub.b B.sub.x M'.sub.y

where M' is one or more elements selected from a group consisting of Ti,V, Nb, Ta, Mo and W and contains Nb, 75≦b≦93 atom %, 6.5≦x≦14 atom % and4≦y≦9 atom %.
 8. A method of manufacturing a Fe-base soft magnetic alloyaccording to claim 2, wherein said Fe-base soft magnetic alloy iscomposed as expressed by the following formula:

    Fe.sub.b B.sub.x M'.sub.y X.sub.u

where M' is one or more elements selected from a group consisting of Ti,V, Nb, Ta, Mo and W and contains Nb, X is one or more elements selectedfrom a group consisting of Cr, Ru, Rh and Ir, 75≦b≦93 atom %, 6.5≦x≦14atom %, 4≦y≦9 atom % and u≦5 atom %.
 9. A method of manufacturing aFe-base soft magnetic alloy according to claim 2, wherein said Fe-basesoft magnetic alloy is composed as expressed by the following formula:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M'.sub.y

where Z is Co and/or Ni, M' is one or more elements selected from agroup consisting of Ti, V, Nb, Ta, Mo and W and contains Nb, a≦0.1,75≦b≦93 atom %, 6.5≦x≦14 atom % and 4≦y≦9 atom %.
 10. A method ofmanufacturing a Fe-base soft magnetic alloy according to claim 2,wherein said Fe-base soft magnetic alloy is composed as expressed by thefollowing formula:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M'.sub.y X.sub.u

where Z is Co and/or Ni, M' is one or more elements selected from agroup consisting of Ti, V, Nb, Ta, Mo and W and contains Nb, X is one ormore elements selected from a group consisting of Cr, Ru, Rh and Ir,a≦0.1, 75≦b≦93 atom %, 6.5≦x≦14 atom %, 4≦y≦9 atom % and u≦5 atom %. 11.A method of manufacturing a Fe-base soft magnetic alloy according toclaim 2, wherein said Fe-base soft magnetic alloy is composed asexpressed by the following formula:

    Fe.sub.b B.sub.x M.sub.y T.sub.z

where M is one or more elements selected from a group consisting of Ti,Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf, T is one or moreelements selected from a group consisting of Cu, Ag, Au, Pd, Pt and Bi,75≦b≦93 atom %, 0.5≦x≦18 atom %, 4≦y≦10 atom % and z≦4.5 atom %.
 12. Amethod of manufacturing a Fe-base soft magnetic alloy according to claim11, wherein 0.2≦z≦4.5 atom %.
 13. A method of manufacturing a Fe-basesoft magnetic alloy according to claim 2, wherein said Fe-base softmagnetic alloy is composed as expressed by the following formula:

    Fe.sub.b B.sub.x M.sub.y T.sub.z X.sub.u

where M is one or more elements selected from a group consisting of Ti,Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf, T is one or moreelements selected from a group consisting of Cu, Ag, Au, Pd, Pt and Bi,X is one or more elements selected from a group consisting of Cr, Ru, Rhand Ir, 75≦b≦93 atom %, 0.5≦x≦18 atom %, 4≦y≦10 atom %, z≦4.5 atom % andu≦5.0 atom %.
 14. A method of manufacturing a Fe-base soft magneticalloy according to claim 13, wherein 0.2≦z≦4.5 atom %.
 15. A method ofmanufacturing a Fe-base soft magnetic alloy according to claim 2,wherein said Fe-base soft magnetic alloy is composed as expressed by thefollowing formula:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M.sub.y T.sub.z

where Z is Co and/or Ni, M is one or more elements selected from a groupconsisting of Ti, Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf,T is one or more elements selected from a group consisting of Cu, Ag,Au, Pd, Pt and Bi, a≦0.1, 75≦b≦93 atom %, 0.5≦x≦18 atom %, 4≦y≦10 atom %and z≦4.5 atom %.
 16. A method of manufacturing a Fe-base soft magneticalloy according to claim 15, wherein 0.2≦z≦4.5 atom %.
 17. A method ofmanufacturing a Fe-base soft magnetic alloy according to claim 2,wherein said Fe-base soft magnetic alloy is composed as expressed by thefollowing formula:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M.sub.y T.sub.z X.sub.u

where Z is Co and/or Ni, M is one or more elements selected from a groupconsisting of Ti, Zr, Hf, V, Nb, Ta, Mo and W and contains Zr and/or Hf,T is one or more elements selected from a group consisting of Cu, Ag,Au, Pd, Pt and Bi, X is one or more elements selected from a groupconsisting of Cr, Ru, Rh and Ir, a≦0.1, 75≦b≦93 atom %, 0.5≦x≦18 atom %,4≦y≦10 atom %, z≦4.5 atom % and u≦5 atom %.
 18. A method ofmanufacturing a Fe-base soft magnetic alloy according to claim 17,wherein 0.2≦z≦4.5 atom %.
 19. A method of manufacturing a Fe-base softmagnetic alloy according to claim 2, wherein said Fe-base soft magneticalloy is composed as expressed by the following formula:

    Fe.sub.b B.sub.x M'.sub.y T.sub.z

where M' is one or more elements selected from a group consisting of Ti,V, Nb, Ta, Mo and W and contains any one of Ti, Nb and Ta, T is one ormore elements selected from a group consisting of Cu, Ag, Au, Pd, Pt andBi, 75≦b≦93 atom %, 6.5≦x≦18 atom %, 4≦y≦10 atom % and z≦4.5 atom %. 20.A method of manufacturing a Fe-base soft magnetic alloy according toclaim 19, wherein 0.2≦z≦4.5 atom %.
 21. A method of manufacturing aFe-base soft magnetic alloy according to claim 2, wherein said Fe-basesoft magnetic alloy is composed as expressed by the following formula:

    Fe.sub.b B.sub.x M'.sub.y T.sub.z X.sub.u

where M' is one or more elements selected from a group consisting of Ti,V, Nb, Ta, Mo and W and contains any one of Ti, Nb and Ta, T is one ormore elements selected from a group consisting of Cu, Ag, Au, Pd, Pt andBi, X is one or more elements selected from a group consisting of Cr,Ru, Rh and Ir, 75≦b≦93 atom %, 6.5≦x≦18 atom %, 4≦y≦10 atom %, z≦4.5atom % and u≦5 atom %.
 22. A method of manufacturing a Fe-base softmagnetic alloy according to claim 21, wherein 0.2≦z≦4.5 atom %.
 23. Amethod of manufacturing a Fe-base soft magnetic alloy according to claim2, wherein said Fe-base soft magnetic alloy is composed as expressed bythe following formula:

    (Fe.sub.1-a z.sub.a).sub.b B.sub.x M'.sub.y T.sub.z

where Z is Co and/or Ni, M' is one or more elements selected from agroup consisting of Ti, V, Nb, Ta, Mo and W and contains any one of Ti,Nb and Ta, T is one or more elements selected from a group consisting ofCu, Ag, Au, Pd, Pt and Bi, a≦0.1, 75≦b≦93 atom %, 6.5≦x≦18 atom %,4≦y≦10 atom % and z≦4.5 atom %.
 24. A method of manufacturing a Fe-basesoft magnetic alloy according to claim 23, wherein 0.2≦z≦4.5 atom %. 25.A method of manufacturing a Fe-base soft magnetic alloy according toclaim 2, wherein said Fe-base soft magnetic alloy is composed asexpressed by the following formula:

    (Fe.sub.1-a Z.sub.a).sub.b B.sub.x M'.sub.y T.sub.z X.sub.u

where Z is Co and/or Ni, M' is one or more elements selected from agroup consisting of Ti, V, Nb, Ta, Mo and W and contains any one of Ti,Nb and Ta, T is one or more elements selected from a group consisting ofCu, Ag, Au, Pd, Pt and Bi, X is one or more elements selected from agroup consisting of Cr, Ru, Rh and Ir, a≦0.1, 75≦b≦93 atom %, 6.5≦x≦18atom %, 4≦y≦10 atom %, z≦4.5 atom % and u≦5 atom %.
 26. A method ofmanufacturing a Fe-base soft magnetic alloy according to claim 25,wherein 0.2≦z≦4.5 atom %.
 27. A method of manufacturing a Fe-base softmagnetic alloy according to claim 1, wherein the step of subjecting theamorphous alloy ribbon to heat treatment comprises heating the amorphousalloy ribbon at a heating rate of 40° C./minute or higher.